Two goals in the opening half hour seemingly had the Galaxy on their way to a comfortable win, but the outcome arguably belied the overall performance, with LAFC on the wrong end of three disallowed goals.
Carlos Vela was ruled offside twice along with Latif Blessing, whose late equaliser was chalked off in the eighth minute of injury time, after Cristian Arango pulled one back in the 79th minute.
Samuel Grandsir assisted twice for the Galaxy, with his first a pinpoint cross at the back post for Javier Hernandez, who cunningly drifted off Mamadou Fall's shoulder in 13th minute.
A second from Sega Coulibaly ultimately proved sufficient, as the Galaxy moved to four wins and one defeat in games where they scored the opening goal in the MLS this season.
The win puts them a point off LAFC in the Western Conference and tied for second with Real Salt Lake, who failed to move to top spot with a 2-2 draw to Toronto.
Philadelphia Union remained top of the Eastern Conference, meanwhile, after their 1-0 win over Columbus Crew.
Union took the lead in only the second minute and in calamitous circumstances, with Crew keeper Eloy Room mishandling a cross into the box, before the ball trickled into his own net.
Jim Curtin's side was content to absorb pressure as the Crew spent the rest of the match trying to break them down, and failed to create anything of substance.
Orlando City moved to second in the East with a 1-0 win over a ten-man Chicago Fire, leapfrogging New York Red Bulls, who lost 2-1 at home to Montreal.
In the other early game on the East Coast, a Leonardo Campana hat-trick gave Inter Miami their first win of the season, in a 3-2 victory over New England Revolution.
In the later games on Saturday, Nashville defeated Sporting KC 2-1, while Houston Dynamo fought from a 2-1 deficit to defeat San Jose Earthquakes 4-3.
Goals from Brandon Servania and Jesus Ferreira on either side of the interval handed Dallas an eventual 3-1 win over Colorado Rapids.
LAFC crushed the Whitecaps 6-0 at Banc of California Stadium on Wednesday, thanks to five goals in the opening 33 minutes.
The five goals scored in 32 minutes, 13 seconds was the fastest a team has netted five from kick-off in MLS history, according to Opta.
The Seattle Sounders had set the previous record (32:43) just 13 days ago against the San Jose Earthquakes.
LAFC went ahead in the second minute through Dejan Jakovic, who headed in a Brian Rodriguez corner.
Another corner led to Bradley Wright-Phillips finishing before the veteran forward produced another acrobatic effort in the 11th minute.
Things went from bad to worse for Vancouver when Ranko Veselinovic turned in a Rodriguez cross just three minutes later.
Diego Rossi made it 5-0 after a one-two with Mark-Anthony Kaye in the 33rd minute.
LAFC would have to wait until the second half for a sixth, Rodriguez's cross from the right leading to an Andy Rose own goal.
The win saw Los Angeles climb into sixth in the Western Conference, while Vancouver are ninth.
Orlando City extended their unbeaten run to seven games with a 2-1 win over Sporting Kansas City.
Tesho Akindele and Benji Michel scored before half-time and Orlando held on despite Johnny Russell's 53rd-minute strike.
The Earthquakes' struggles continued with a 5-0 loss to the Colorado Rapids.
San Jose have conceded five goals in a match five times this season, which is the most allowed by a team in a single campaign, according to Opta. The Earthquakes are just 13 games into their season.
Chicago Fire recorded a 4-0 win over the Houston Dynamo, while Inter Miami slumped to a 4-1 defeat against the New York Red Bulls.
History was made as Nashville beat DC United 1-0, with Tori Penso becoming the first female referee to oversee an MLS game in 20 years.
Columbus Crew retained their five-point lead atop the Eastern Conference thanks to a 2-1 win over Minnesota United.
The New England Revolution beat Montreal Impact 3-1, Toronto edged New York City 1-0 and Atlanta United overcame Dallas 1-0.
Cincinnati and Philadelphia Union played out a 0-0 draw, Real Salt Lake enjoyed a 2-0 win over the LA Galaxy and the Portland Timbers edged the Seattle Sounders 1-0.
Though the visitors hit the lead twice in the first half at Exploria Stadium, the Lions equalised as many times, including a finely taken goal from Alexandre Pato in the 36th minute.
Sensing where the ball would drop following Mauricio Peyeyra's ball over and into the penalty area, Pato set himself and calmly volleyed past Maxime Crepeau.
Ilie Sanchez rifled home a mere six minutes into the second half and from there, LAFC were able to sit and absorb Orlando pressure.
After some important saves from Crepeau to deny a third equaliser, substitute Kwadwo Opoku was able to score an injury-time sealer in transition, moving Steve Cherundolo's side to four wins and a draw from five games.
Meanwhile, Philadelphia Union were able to keep their place atop the Eastern Conference, with a 2-0 win at home to Charlotte FC.
The Union took the lead after only four minutes and in uncomplicated fashion, with Sergio Santos running on to a ball over the top and assisting for Julian Carranza from the byline.
Daniel Gazdag doubled the margin a minute within the restart, and similarly to LAFC, absorbed pressure in their defensive half to see out the win to move to 13 points from five games.
NY Red Bulls and Atlanta stayed within three points of Philadelphia in the Eastern Conference with respective 1-0 victories over New England Revolution and DC United. Columbus Crew dropped points at home to Nashville, with Alex Muyl's lone goal the difference.
A Gonzalo Higuain penalty would not suffice for Inter Miami, who remain rooted to the bottom of the ladder in the East, after Phil Neville's side losing 3-1 to Houston Dynamo. Chicago Fire and FC Dallas played out a goalless draw, while Toronto FC beat reigning MLS Cup champions New York City 2-1.
In the Western Conference, Real Salt Lake fell two points behind with a 1-1 draw away to Colorado, Austin FC conceded two goals in as many minutes to eventually play out a 2-2 draw against San Jose Earthquakes.
Ryan Raposo's 73rd-minute winner was enough for Vancouver Whitecaps at home to Sporting KC, while Brent Kallman's own goal eventually condemned Minnesota to their first defeat of the season, losing 2-1 to the Seattle Sounders.
LAFC led twice in the first half at Exploria Stadium but were pegged back on both occasions, first by a finely taken goal from Alexandre Pato in the 36th minute.
Sensing where the ball would drop following Mauricio Peyeyra's delivery into the penalty area, Pato set himself and calmly volleyed past Maxime Crepeau.
But Ilie Sanchez rifled in a third LAFC goal six minutes into the second half and the visitors were able to absorb Orlando pressure thereafter.
After some important saves from Crepeau, substitute Kwadwo Opoku sealed victory in stoppage time, moving Steve Cherundolo's side to 13 points from five games after four wins and a draw.
Meanwhile, Philadelphia Union were also able to keep their place atop the Eastern Conference with a 2-0 win at home to Charlotte FC.
The Union took the lead in uncomplicated fashion after only four minutes, with Sergio Santos running onto a ball over the top and crossing for Julian Carranza from the byline.
Daniel Gazdag doubled the lead a minute into the second half, with that two-goal margin enough for the Union to see out the win and themselves move to 13 points.
New York Red Bulls and Atlanta United stayed within three points of Philadelphia in the East with respective 1-0 victories over New England Revolution and DC United. Columbus Crew lost at home to Nashville, with Alex Muyl's lone goal the difference.
A Gonzalo Higuain penalty counted for little for Inter Miami, who remain rooted to the bottom of the ladder in the East after Phil Neville's side lost 3-1 to Houston Dynamo. Chicago Fire and FC Dallas played out a goalless draw, while Toronto FC beat reigning MLS Cup champions New York City 2-1.
CF Montreal edged FC Cincinnati in a seven-goal thriller, trailing twice in the first half before recovering to win 4-3.
In the Western Conference, Real Salt Lake fell two points behind with a 1-1 draw away to Colorado Rapids, while Austin FC conceded two goals in as many minutes to draw 2-2 against San Jose Earthquakes.
Ryan Raposo's 73rd-minute winner was enough for Vancouver Whitecaps at home to Sporting Kansas City, while Brent Kallman's own goal ultimately condemned Minnesota United to their first defeat of the season, losing 2-1 to Seattle Sounders.
After three straight losses in all competitions, Los Angeles FC responded by thrashing the San Jose Earthquakes 5-1 at Banc of California Stadium.
Diego Rossi's beautiful finish into the corner opened the scoring after a poor turnover of possession by the Earthquakes in the 21st minute.
But LAFC had to wait until the second half to truly take control.
Another bad turnover allowed Bradley Wright-Phillips through to double the lead, before Jose Cifuentes made it 3-0.
Rossi added his second in the 69th minute before Danny Musovski made it 5-0, Danny Hoesen later adding a consolation goal for San Jose.
The win lifted LAFC up into third in the Western Conference, with San Jose sitting 11th.
The Galaxy made it three straight wins by edging the Portland Timbers 3-2 at Providence Park.
Efrain Alvarez opened the scoring for the Galaxy, completing a fine team move with a finish into the top corner from inside the area.
It took until five minutes into the second half for the visitors to double their lead through Cristian Pavon's individual effort.
Felipe Mora gave Portland hope with a 67th-minute goal, but Joe Corona struck for the Galaxy with a wonderful 20-yard strike.
Diego Valeri came off the bench to add a second for Portland in additional time.
The Timbers are sixth in the Western Conference, one spot behind the Galaxy while being level on points.
Columbus Crew returned to the top of the Eastern Conference after a 1-0 win over Philadelphia Union.
Lucas Zelarayan's deflected 25-yard effort in the 55th minute was enough for Columbus.
Elsewhere, Western Conference leaders Sporting Kansas City were held to a 1-1 draw by Dallas.
Real Salt Lake and the Seattle Sounders drew 2-2 in a clash that featured a screamer from Pablo Ruiz, while Orlando City played out a 1-1 draw with Nashville.
New York City overcame New England Revolution 2-0, Houston Dynamo beat Minnesota United 3-0 and Erik Sorga scored a 98th-minute winner for DC United as they edged the New York Red Bulls 1-0.
Atlanta United and Inter Miami drew 0-0, while Cincinnati's clash with Chicago Fire also finished goalless.
Montreal trailed 2-0 after 14 minutes and 4-2 after 46 minutes, but Ahmed Hamdi scored twice in the final 16 minutes to give the home side a wild victory.
In Nashville, Hany Mukhtar scored in the 10th, 13th and 16th minutes on the way to a 5-1 rout of Chicago Fire.
The six-minute span was the second-shortest for a hat-trick in MLS history after LA Galaxy's Harut Karapetyan needed just five minutes to score three in a 1998 match.
Gustavo Bou's team-leading seventh goal gave New England Revolution a 1-0 win at Atlanta United, snapping a three-game win drought for the Eastern Conference leaders.
Second-half goals from Deiber Caicedo and Cristian Dajome gave Vancouver just their third win from 13 games this season, a 2-1 triumph over LA Galaxy.
Darlington Nagbe's impressive individual effort opened the scoring in a 2-1 Columbus Crew win over New York City FC.
Nani's 77th-minute penalty gave Orlando City a 1-1 draw with Toronto after Jozy Altidore had opened the scoring five minutes earlier, while Cole Bassett's second-half goal for Colorado Rapids earned a 1-1 draw against San Jose.
Kacper Przybylko's 83rd-minute decider gave Philadelphia Union a 2-1 victory over DC United, while Jeremy Ebobisse scored in the 84th minute to lift Portland past Dallas 1-0.
Carlos Vela's left-footed rocket in the 79th minute was the difference in LAFC's 2-1 home win over Real Salt Lake.
The New York Red Bulls-Inter Miami match was postponed due to weather.
Columbus made it five wins in six MLS games this season with a 3-0 victory over Chicago Fire on Thursday.
Gyasi Zardes scored and also missed a penalty as Darlington Nagbe scored a stunner at MAPFRE Stadium.
Derrick Etienne found the bottom corner from a Milton Valenzuela pass to open the scoring for Columbus in the 20th minute.
Zardes put a penalty over the crossbar just before half-time and Columbus left it late to seal their win.
Nagbe flicked the ball up to himself 30 yards from goal before unleashing a stunning volley into the corner to make it 2-0.
Zardes sealed the win in the 88th minute, tapping in Pedro Santos' cross as the Crew moved four points clear atop the conference.
The Hudson River Derby went the Red Bulls' way as they recorded a 1-0 win over New York City.
Kyle Duncan's powerful 20-yard strike just before the hour-mark was spilled by City goalkeeper Sean Johnson and awarded after a VAR review.
The Red Bulls are third in the Eastern Conference, while New York City are second last.
In the day's other game, New England Revolution and Philadelphia Union drew 0-0.
Former Manchester United attacker Nani scored and provided an assist in Orlando's 4-1 thrashing of the Chicago Fire on Saturday.
After Chris Mueller opened the scoring, he crossed for Nani to head in a second in the 24th minute.
Given a chance to get back into the game, Chicago squandered it when Alvaro Medran had a penalty well saved by Pedro Gallese.
Chicago took their next chance from the spot through Robert Beric early in the second half, but Orlando sealed their win late.
Junior Urso scrambled in from inside the area after Nani's set-piece went uncleared, and the Portuguese attacker's pass later found Benji Michel to finish off in additional time.
Orlando are second in the Eastern Conference, five points behind the high-flying Columbus Crew.
Second-half goals from Pedro Santos and Gyasi Zardes saw Columbus record a 2-0 win over Nashville.
Diego Valeri netted a brace as the Portland Timbers crushed the San Jose Earthquakes 6-1 at Avaya Stadium.
Fresh off confirming the signing of Gonzalo Higuain, Inter Miami recorded a second win in three matches by beating Atlanta United 2-1.
Elsewhere, a 10-man LA Galaxy fell to the Colorado Rapids 2-0 and Dallas also finished with 10 but recorded a 3-2 win over Sporting Kansas City.
Haris Medunjanin scored directly from a corner in the 85th minute as Cincinnati beat the New York Red Bulls 1-0 and the Vancouver Whitecaps beat a 10-man Real Salt Lake 2-1.
New York City drew 0-0 with the New England Revolution, DC United and Toronto played out a 2-2 draw, while the Houston Dynamo and Minnesota United did likewise.
Former Manchester United winger Nani scored his ninth goal of the MLS season as Orlando City missed the chance to close the gap at the top after a 1-1 draw at Cincinnati on Saturday.
Cincinnati, who were winless in their past seven games coming in, opened the scoring in the 42nd minute from Brazilian attacker Brenner.
Nani levelled moments after being brought into the game as a 55th-minute substitute, driving forward and firing in a low left-foot pinpoint shot.
The result means back-to-back draws for Orlando who are second in the Eastern Conference, seven points behind leaders New England.
Third-placed New York City blew an early two-goal lead to draw 2-2 away to Toronto.
Santiago Rodriguez and Ismael Tajouri had put City up 2-0 inside 21 minutes but Toronto netted twice after the break.
Richie Laryea pulled one back in the 49th minute before reigning MVP Alejandro Pozuela equalised in the 55th minute with a tap in.
Portland Timbers beat Real Salt Lake 3-2 in a see-sawing contest with Felipe Mora netting the eventual winner.
Columbus Crew suffered their third straight defeat as Ezequiel Barco netted a double for Atlanta City in a 3-2 win.
Dallas continued their good run of recent form, claiming their third win in four games, with a 2-0 triumph over Austin.
Minnesota United won 2-0 over Houston Dynamo, while Colorado Rapids drew 0-0 with Western Conference leaders Sporting KC.
The Portuguese got on the end of Dutchman Silvester van der Water's 87th-minute cross for the winner which keeps Orlando in touch with Eastern Conference leaders New England.
Atlanta had taken a first-minute lead from Josef Martinez's perfectly placed long-range effort, but Kyle Smith equalised on the stroke of half-time from Nani's corner.
Marcelino Moreno restored United's lead in the 66th minute with a stunning curling strike from outside of the box.
Orlando put together a fine team goal to square the game up in the 79th minute as van der Water headed in Benji Michel's pass.
The Dutch substitute would then provide the pass for Nani's decisive goal, which was his seventh strike of the season.
New York City stayed close behind Orlando in the Eastern Conference with their third consecutive win, a 4-1 victory over Columbus Crew.
City piled on the style, racing to a 2-0 half-time lead after strikes from Valentin Castellanos's early header and Thiago's chip.
Keaton Parks added a third with a deft 51st-minute touch, meaning it was the first time all season Columbus had conceded three goals in a game.
Santiago Rodriguez bundled in from close-range albeit requiring a VAR review, before Pedro Santos' consolation penalty.
LA Galaxy, without Javier Hernandez, cruised past Portland Timbers 4-1 to solidify their grip on third in the west.
Malagasy midfielder Rayan Raveloson pulled off a spectacular overheard volley to open the scoring.
Tesho Akindele scored the fastest goal in club history as Orlando got off to a quick start at home to Jaap Stam's Cincinnati on Saturday.
Akindele found the back of the net after just 33 seconds, surpassing the Orlando record set by Chris Mueller (62 seconds) in April 2018.
Nani doubled the lead in stunning fashion in the 19th minute – the former Manchester United star leaving Yuya Kubo on the floor after cutting to his right foot and then his left as he curled the ball past Przemyslaw Tyton.
After Nani hit the post minutes later and saw his shot saved by Cincinnati goalkeeper Tyton just past the hour mark, Junior Urso sealed the victory with 10 minutes remaining.
Orlando – who remain unbeaten through three games – are third in the Eastern Conference, behind leaders New England Revolution and second-placed New York City.
The Revolution edged Atlanta United 2-1 and New York City defeated reigning Supporters' Shield winners Philadelphia Union 2-0.
The Earthquakes and Dallas, meanwhile, both won 4-1 against DC United and Portland Timbers respectively.
Jackson Yueill's brace and a pair of assists from Cade Cowell fuelled the Earthquakes, who are top of the Western Conference on goal difference but level on points with Real Salt Lake, LA Galaxy and Austin FC.
Dallas showed no mercy at home to the Timbers after Andres Ricaurte and Jader Obrian scored in the opening 13 minutes.
Real Salt Lake came from behind to top Sporting Kansas City 3-1 courtesy of Rubio Rubin's second-half double, while MLS newcomers Austin prevailed 1-0 against Minnesota United.
Elsewhere, New York Red Bulls were 2-0 winners over Chicago Fire, defending champions Columbus Crew were held to a goalless draw by Montreal Impact and Houston Dynamo and Los Angeles FC played out a 1-1 draw.
A last-gasp 1-1 draw against New York Red Bulls was enough for Orlando to secure a place in the MLS Cup play-offs on Sunday.
Orlando were stunned in stoppage time – Brian White's 95th-minute equaliser cancelling out Nani's 56th-minute penalty at Red Bull Arena.
But after Toronto edged Atlanta United 1-0, Orlando were assured of their first trip to the play-offs, having entered the league in 2015.
"We've put ourselves in a good position," Orlando forward Daryl Dike said. "Obviously we just made the play-offs today, but I think we're going to carry on. The goal wasn't just playoffs. We're not done now. We just keep going and keep going.
"We want three points every single game and we want to finish the highest in the table. That's the main goal."
Orlando – fourth in the Eastern Conference – are in the midst of a club-record 12-game unbeaten streak, per Stats Perform.
The Crew's 3-1 win over New York City, coupled with Toronto's triumph, sent the team back to the play-offs after missing out last season.
Columbus also snapped a four-match winless streak to move third in the east, two points ahead of Orlando and a point behind second-placed Philadelphia Union.
Elsewhere, LA Galaxy ended a six-game losing skid by topping Vancouver Whitecaps 1-0 thanks to substitute Kai Koreniuk's late winner.
Koreniuk became the first substitute to score for the Galaxy this season – the Los Angeles club were the only team without a goal from a substitute in 2020.
Los Angeles FC's Christian Torres (16 years, six months and three days) became the youngest player to score in MLS since Sporting Kansas City's Gianluca Busio (16 years, four months and 20 days) in 2018, according to Stats Perform.
Torres' last-gasp equaliser earned LAFC a 1-1 draw at Western Conference high-flyers Portland Timbers.
Seattle Sounders drew 0-0 with San Jose Earthquakes, Houston Dynamo played out a 2-2 draw against Minnesota United and DC United beat FC Cincinnati 2-1.
Bruce Arena's side, who clinched their first-ever Supporters' Shield on Saturday, won thanks to Tajon Buchanan's 74th-minute strike.
The result took Revolution's season tally to 73 points from 33 games, eclipsing the previous record mark held by LAFC with 72 points in 2019.
New England have one more regular season match to extend their record, playing Inter Miami at home on November 7.
Canada international Buchanan came up with the winner, showing fast feet to make space for a low shot that beat Rapids goalkeeper William Yarbrough, who had sensationally kept out Henry Kessler from close range minutes earlier.
New York Red Bulls slipped out of the Eastern Conference play-offs spots after a 1-0 defeat to DC United who moved above them into seventh place.
United snapped a four-game winless skid, while also ending the Red Bulls' four-game running run and eight-game unbeaten streak in the process. Kevin Paredes side-footed home the ninth-minute winner for United.
Sporting KC moved into top spot in the Western Conference and dented LA Galaxy's play-offs aspirations with a 2-0 win.
Johnny Russell extended his scoring run to eight straight games with both goals for KC who clinched a top-four seeding as well.
Randall Leal scored two goals and grabbed an assist as Nashville came from two goals down twice to win 6-3 at Cincinnati.
Portland Timbers moved in the west's top four with a 2-0 home victory over San Jose Earthquakes, while Vancouver Whitecaps climbed up to fifth with a 2-1 triumph over Minnesota United.
New York City boosted their Eastern Conference top-four seed hopes with a 1-0 home win over Chicago Fire, while Josef Martinez's winner helped Atlanta United past Inter Miami 2-1 after Gonzalo Higuain had opened the scoring from the spot.
Columbus Crew upset Orlando City 3-2, Toronto held Philadelphia Union 2-2 as Jozy Altidore netted while Real Salt Lake scored twice in the final 10 minutes to win 2-1 at Dallas.
The Revolution improved their record, with back-to-back wins, to the best in the MLS with 30 points from 15 games, sitting atop the Eastern Conference.
Inter are bottom of the east, with only eight points from 14 games, having lost their past six.
Carles Gil provided the assist, his 11th of the season, for Traustason's 15th-minute header, before Teal Bunbury fired in a 27th minute goal from Inter goalkeeper Nick Marsman's parry.
Icelandic midfielder Traustason grabbed his second in the 36th minute, whipping in a shot after a goalmouth scramble from a corner.
Gil was crafty on the right side of the box before setting up another goal with Adam Buksa lashing home a fine volley on the stroke of half-time.
Buksa grabbed a double in the 83rd minute as Gustavo Bou put him into space with the Polish striker finishing with class.
Without Javier Hernandez, LA Galaxy came from two goals down to claim a 2-2 draw away to Real Salt Lake.
Albert Rusnak and Maikel Chang had scored inside the opening 25 minutes to give RSL a 2-0 lead.
Victor Vazquez pulled one back with a top-corner strike in the 33rd minute, before RSL keeper David Ochoa had spectacularly saved a second-half Rayan Raveloson header.
But Madagascar talent Raveloson headed in a 77th-minute equaliser to earn a share of the spoils.
DC United scored twice in the final 10 minutes to rescue a 2-2 draw at struggling Chicago Fire.
Gaston Gimenez's 32nd-minute strike, on his return from the Copa America, and Andy Najar's 61st-minute own goal had Chicago on track but United hit back late.
In the 82nd minute, Yordy Reyna laid off for Kevin Paredes who fired in off the post, before Ola Kamara converted an 87th-minute penalty.
Hungarian forward Daniel Salloi netted a 94th minute equalizer for high-flying Sporting KC to claim a 1-1 home draw with 10-man San Jose Earthquakes who are winless in 10.
Salloi forced home a rebound after Johnny Russell's free-kick hit the woodwork after Nathan had headed the Earthquakes ahead from a corner against the run of play early in the second half.
Felipe Mora glanced on a late winner for Portland Timbers to edge Los Angeles FC 2-1 after Carlos Vela had earlier squared up following Diego Valeri's 100th goal for the club.
Colorado Rapids eased past Dallas 2-0 to extend their unbeaten run, Cincinnati drew 1-1 with Atlanta United and Columbus Crew and Nashville played out a goalless draw.
Toronto drew 1-1 with New York Red Bulls, while New York City edged Montreal 1-0.
After failing to score in their opening two games – a 1-0 loss to LA Galaxy and a goalless draw with Vancouver Whitecaps – City hit the lead after only seven minutes, with Alexander Callens rifling home after Montreal failed to clear their lines from a corner.
Santiago Rodriguez spectacularly chipped Sebastian Breza to double the margin on 20, but only after Montreal gifted City possession in an attempt to play out from their own half.
Zachary Brault-Guillard pulled one back for CFM, but following further City goals from Telles Magno and Thiago Andrade, the scoreline arguably belied the performance.
Douglas Costa opened his account in the MLS later on Saturday, scoring the equaliser in LA Galaxy's 3-2 loss away to Seattle Sounders.
Javier Hernandez gave the Galaxy a shock lead in the sixth minute, after fine link-up play between Raheem Edwards and Kevin Cabral, but the Sounders fought back to lead before the interval – with goals from Jordan Morris and Fredy Montero.
Costa drew the visitors level from the dead ball after 48 minutes, wrong-footing Stefan Frei, but Xavier Arreaga headed home in the 72nd to give the Sounders their first win of the season.
Los Angeles FC continued their unbeaten start to the season, meanwhile, grinding out a 2-0 win against a 10-man Inter Miami at DRV PNK Stadium.
A deflected Carlos Vela pass put Kwadwo Opoku through on the stroke of the interval, and the 20-year-old Ghanaian finished with composure. That didn't spell the end of events in the first half, though, as Brek Shea was given a straight red card in injury time.
LAFC had six shots for the match compared Inter's seven, despite 53 per cent possession and an extra man. However, an Ismael Tajouri free-kick crept inside Inters back post in the 82nd minute to secure the win.
Steve Cherundolo's side are equal top in the Western Conference with Real Salt Lake, who defeated New England Revolution 3-2. Austin FC couldn't keep pace in the final Saturday game, however, going down 1-0 away to Portland Timbers through a Bill Tuiloma goal.
Columbus Crew share the lead in the Eastern Conference, following their 2-1 win over Toronto FC. They are joined by Philadelphia Union, who defeated San Jose Earthquakes 2-0.
A Darwin Quintero brace handed Houston Dynamo a 2-0 win against Vancouver Whitecaps, while Brandon Vazquez scored a double of his own in FC Cincinnati's 2-1 win at Orlando City.
FC Dallas, Chicago Fire and Colorado Rapids respectively secured 2-0 victories over Nashville, DC United and Sporting Kansas City in Saturday's other games.
Tesho Akindele's header after 12 minutes to give Orlando City a 1-0 victory against Toronto FC, giving the Florida side three wins and three draws through six matches.
The Revolution saw off 10-man New York Red Bulls 3-1 behind first-half goals from Gustavo Bou and Tajon Buchanan and an Adam Buksa tally late to seal it.
Two late strikes from Lucas Zelarayan helped the Columbus Crew stun New York City FC 2-1 after the home side led into the 82nd minute.
Felipe Mora's second-half brace and a penalty from Diego Valeri lifted Portland to a 3-0 triumph over 10-man LA Galaxy.
Diego Rossi scored twice before the break as Los Angeles FC held on to defeat Colorado Rapids 2-1.
Houston's Memo Rodriguez and Maximiliano Urruti provided the winning margin for Houston as they won 2-1 over Vancouver.
Sporting Kansas City continued their strong start, shaking off an early San Jose Earthquakes goal from Javier Lopez en route to a 3-1 win as Jaylin Lindsey, Alan Pulido and Daniel Salloi found the back of the net.
Luka Stojanovic lifted Chicago Fire past Inter Miami 1-0 for their first win of the season, and FC Cincinnati also emerged victorious for the first time this term with a 2-1 win at Montreal.
Real Salt Lake escaped with a 2-2 draw at FC Dallas thanks to Damir Kreilach's goal after 86 minutes.
A 2-1 victory over the Chicago Fire saw Philadelphia push three points clear of Toronto in the Eastern Conference, and for the Supporters' Shield, which they are bidding to win for the first time.
Kacper Przybylko opened the scoring from the penalty spot approaching the half-hour mark, following a handball in the area.
Chicago's chances of a comeback were dealt a blow nine minutes before half-time, Francisco Calvo sent off after a tackle on Alejandro Bedoya.
However, they managed to find an equaliser prior to the break as Robert Beric headed in from close range.
But Philadelphia scored what proved to be the winner in the 65th minute, when Cory Burke headed in a cross from Olivier Mbaizo.
According to Opta, Union became the first team to win their first eight home matches of an MLS season since San Jose in 2002, when the Earthquakes claimed their first 10.
The Timbers clinched a spot in the play-offs thanks to a 5-2 thrashing of the struggling LA Galaxy.
Jaroslaw Niezgoda scored a brace for Portland, who were 3-0 up after 30 minutes following Diego Valeri's penalty.
Eryk Williamson and Andy Polo also netted as the Timbers thrashed the Galaxy, who are bottom of the Western Conference.
Portland became the first team with multiple five-goal games against an opponent in a single MLS season since the Fire against the New York Red Bulls in 2008, having thrashed the Galaxy 6-3 earlier this month.
Chris Wondolowski scored a brace as the Earthquakes enjoyed a 2-0 win over Real Salt Lake.
It was his 24th multi-goal game in MLS. Only Landon Donovan (32) has more.
The New York Red Bulls left it late to edge the New England Revolution 1-0 and reach the play-offs, Sporting Kansas City overcame Cincinnati 1-0 and Orlando City thrashed Atlanta United 4-1.
New York City upset Toronto 1-0, Minnesota United beat the Colorado Rapids 2-1, DC United were too good for Columbus Crew 1-0, Dallas claimed a 2-1 win over Inter Miami and Los Angeles FC were 2-1 victors over the Houston Dynamo to clinch their play-off place.
Javier 'Chicharito' Hernandez scored twice for the Galaxy in a 3-3 draw with Minnesota United on Decision Day, but RSL's last-gasp 1-0 win over Sporting Kansas City changed the landscape of the Western Conference.
RSL pipped the Galaxy – without post-season football for the second straight campaign – to the seventh and final play-off spot on victories for the season via a 95th-minute winner, having finished level on 48 points at the end of 34 rounds.
Minnesota finished fifth to clinch a post-season berth in the west, along with sixth-placed Vancouver Whitecaps, who drew 1-1 against Seattle Sounders.
Seattle's stalemate and Sporting KC's late loss allowed Colorado Rapids to secure top seed in the Western Conference following a 5-2 rout of Los Angeles FC, who were eliminated as a result.
In the Eastern Conference, Orlando City beat Montreal 2-0 for a spot in the play-offs, along with Atlanta United (2-1 over FC Cincinnati) and New York Red Bulls – the latter using a 1-1 draw against Nashville to extend their post-season streak to 12 years.
Supporters' Shield winners New England Revolution lost 1-0 to already eliminated Inter Miami, Portland Timbers eased past lowly Austin 3-0, DC United defeated Toronto 3-1, 10-man New York City drew 1-1 with Philadelphia Union and reigning champions Columbus Crew – who will not defend their title – beat Chicago Fire 2-0.
Chris Wondolowski scored in the San Jose Earthquakes' 1-1 draw against Dallas before the league's all-time leading scorer announced his retirement.
Fabio scored the 79th-minute winner, his second goal of the season, after Coronel had saved Mauricio Pereyra's penalty on the stroke of half-time.
Venezuelan midfielder Cristian Casseres fired in an excellent left-foot strike to open the scoring in the sixth minute but Orlando had a chance to level moments before half-time.
Uruguayan midfielder Pereyra shot low to Coronel's left but the Brazilian dived well and palmed away the spot-kick.
Pereyra partly made up for his miss, laying off the pass for Chris Mueller to equalize high into the back of the net in the 59th minute.
But Fabio held off a defender to fire home to secure the Red Bulls' first road win of the season, moving them up to seventh in the Eastern Conference.
DC United had seven different scorers as they trounced Toronto 7-1, keeping them ahead of the Red Bulls in sixth in the East.
Andy Najar, who did not score one of United's goals, set up two and was named Player of the Match.
Eastern Conference leaders New England Revolution blew a two-goal lead to draw 2-2 away to Columbus Crew.
Goals from Tajon Buchanan and Gustavo Bou had New England on the path to victory but Columbus fought back with Andrew Farrell's comical own goal levelling it up.
LAFC grabbed their maiden road win of the campaign, edging Real Salt Lake 1-0 after Jose Cifuentes' 69th-minute strike from Eddie Segura's pass.
Segura was the hero moments later with a diving goal-line clearance to deny Rubio Mendez's on-target lob.
Houston Dynamo and Cincinnati traded goals inside the opening five minutes in a 1-1 draw. Houston have drawn four games in a row.
Argentine forward Ignacio Aliseda scored twice as Chicago Fire claimed their second win of the season, triumphing 3-0 over Atlanta United.
Inter Miami's struggles continued with a 1-0 defeat away to Montreal. Miami have only managed eight points from 11 games, losing their past five.
Benjamin Kikanovic scored late to earn a 2-2 draw for struggling San Jose Earthquakes at Minnesota United. The Earthquakes are winless in eight.
Charles Sapong's second-minute goal was enough for Nashville to secure a 1-0 home win over fellow Eastern Conference contenders Philadelphia Union.
Clark – aged 17 years, four months and 18 days – became the youngest player to score in his first two MLS appearances on Wednesday, per Opta.
Hours after joining the Red Bulls, Clark capped his debut with a goal in Saturday's 1-0 win over Atlanta United.
Clark became the youngest player to score his maiden goal for the Red Bulls since Jozy Altidore in 2006.
He continued where he left off against Toronto, netting the equaliser with 13 minutes remaining midweek.
Following Alejandro Pozuelo's 23rd-minute penalty, Clark earned the visiting Red Bulls a point by firing a shot into the top corner of the net from outside the box.
The Red Bulls are seventh in the Eastern Conference, while Toronto – already play-off bound – remain top through 18 games.
Elsewhere, reigning Supporters' Shield holders Los Angeles FC and struggling LA Galaxy were beaten.
Lucas Cavallini's brace lifted Vancouver Whitecaps to a 2-1 victory against fourth-placed LAFC.
Canada international Cavallini has now scored in back-to-back games after finding the net just twice in his first 11 MLS matches for the Whitecaps, who climbed up to eighth in the standings and in the play-off positions.
As for the Western Conference's bottom side – the Galaxy – they were swept aside 4-0 by San Jose Earthquakes in the Cali Clasico.
Former Manchester United and Real Madrid striker Javier Hernandez was substituted early in the second half, with the Galaxy only managing four goals in the 652 minutes 'Chicharito' has been on the pitch this season.
It was a sixth consecutive defeat for the slumping Galaxy as the Earthquakes moved within a point of LAFC in the west.
Wednesday's scheduled Minnesota United-Chicago Fire fixture was postponed due to a suspected coronavirus case among Minnesota's team delegation.
In other results, New England Revolution edged Montreal Impact 3-2, FC Cincinnati were 2-1 winners over Columbus Crew, Orlando City and New York City drew 1-1, Atlanta saved a 1-1 draw at Inter Miami, Sporting Kansas City fell 1-0 to Dallas, DC United and Philadelphia Union shared the points in a four-goal clash, Real Salt Lake trumped Portland Timbers 2-1 and Nashville accounted for Houston Dynamo 3-1.
