Martinez equalised via an 86th-minute spot-kick to earn Atlanta a 1-1 draw with the Sounders at Lumen Field in Seattle on Sunday.
The Sounders had taken a sixth-minute lead from Raul Ruidiaz, who headed home Joao Paulo's corner to make it six goals in seven games.
Last season's MLS Cup runners-up Seattle remain undefeated and top of the Western Conference through seven matches, but had their four-game winning run ended as Atlanta – led by former Manchester United and Real Madrid defender Heinze – sit fifth in the east.
Last season's Supporters' Shield winners Philadelphia Union moved up into third in the east with a 1-0 victory away to DC United.
Kacper Przybylko netted the winner on the stroke of half-time for the Union, who are now unbeaten in their past four games.
Jamiro Monteiro laid off a perfectly weighted pass into the box for the Polish attacker to control and convert.
Union goalkeeper Andre Blake made a spectacular second-half save to deny United's 18-year-old midfielder Kevin Paredes with a curled effort from the edge of the box.
Undefeated Nashville edged past newcomers Austin 1-0 courtesy of a 35th-minute volley from Randall Leal.
Jared Stroud thought he had scored a second-half equaliser but it was disallowed by VAR for offside.
Nashville, who drew four of their opening five games, have won two of their past three matches to move up to fourth in the Eastern Conference, while Austin have lost three in a row on the road.
Super sub Ruidiaz came off the bench and scored a delightful game-winning goal just past the hour-mark as the Sounders downed Dallas 1-0 in MLS on Wednesday.
The Sounders were winless in 10 consecutive visits to Dallas (D3 L7, including play-offs) dating back to 2014 – their second-longest winless away run against a single opponent in MLS (11 straight at LA Galaxy from 2010 to 2015).
But Seattle snapped that skid thanks to Ruidiaz as Sporting KC's 1-1 draw with Portland Timbers allowed the Sounders to move top of the west by one point.
Atlanta extended their winning streak to three matches after Ezequiel Barco's first-half goal secured a 1-0 win at home to Toronto.
Since the sacking of head coach Gabriel Heinze following a falling out with star Josef Martinez, Atlanta – who had won successive matches for the first time since the opening two games of the 2020 season entering the fixture – have steadily climbed the table.
Atlanta are three points outside of the play-off positions in the Eastern Conference, which is topped by New England Revolution – 3-2 victors against DC United despite ending the contest with 10 men.
Elsewhere, Rodolfo Pizarro's stoppage-time winner guided Inter Miami to a dramatic 3-2 win against Chicago Fire midweek.
Pizarro struck in the 93rd minute to clinch a third straight home triumph for David Beckham's Inter Miami, who have now lost just once in their last six games.
Philadelphia Union and New York Red Bulls were 1-0 winners over New York City and Columbus Crew respectively, Vancouver Whitecaps topped Austin 2-1, Real Salt Lake defeated Houston Dynamo by the same scoreline, 10-man Montreal drew 0-0 with Cincinnati, while Nashville and Orlando City played out a 1-1 draw.
After Raul Ruidiaz's 40th minute opener, the visitors had taken the lead after goals from Cristian Dajome and Lucas Cavallini.
Medranda intervened with his 71st minute strike, coming after a corner was cleared into his path, lashing home from the edge of the box.
The result means Seattle remain top in the Western Conference, having conceded only seven goals in 11 games.
It also ends Vancouver's five-game losing streak, although they remain second last in the west.
Former Manchester United striker Javier 'Chicharito' Hernandez scored a double to lift LA Galaxy to a 3-1 win away to San Jose Earthquakes.
The Mexico international opened the scoring in the 11th minute when he swept home Samuel Grandsir's dangerous cross from the right.
Hernandez produced a similar finish to double their advantage in the 50th minute, tapping home from Kevin Cabral's ball.
Galaxy are third in the Western Conference, four points behind Seattle with a game in hand.
Philadelphia Union extended their unbeaten run to eight games with a 3-3 draw away to Chicago Fire.
Toronto's struggles continued with a 2-0 home defeat to Cincinnati, condemning them to five consecutive defeats.
Sporting Kansas City defeated Los Angeles FC 2-1, Real Salt Lake and Houston Dynamo drew 1-1, Minnesota United won 1-0 at Portland Timbers and Abu Danladi netted a late leveller to help Nashville claim a 1-1 home draw with Montreal.
Cristian Roldan, Jimmy Medranda and Joao Paolo scored in a three-goal first half to inspire the Sounders against the Rapids in Seattle.
The Rapids were enjoying their second-best unbeaten run in club history, only behind the 15-game undefeated streak from April 2016 to July 2016.
But Colorado came unstuck away to the Sounders at Lumen Field, where Roldan broke the deadlock in the second minute before Medranda and Paolo's moment of individual brilliance made it 3-0 prior to half-time.
The Sounders are top of the west, two points clear of Sporting Kansas City, who beat Houston Dynamo 4-2 behind Daniel Salloi's magical performance (one goal and an assist) and Johnny Russell's brace.
Entering the contest, Salloi and Russell had been directly involved, either together or individually, in Sporting KC's previous seven goals (Salloi three goals, Russell three goals and two assists). At least one of those two players had scored or assisted on 19 of the 23 goals Kansas City scored since late July.
David Beckham's Inter Miami and their hopes of featuring in the play-offs were dealt a blow following a 1-0 defeat to Portland Timbers.
Jaroslaw Niezgoda struck to extend Portland's unbeaten run to eight matches, including seven wins, and condemn Inter Miami to a fourth consecutive loss.
Inter Miami are eight points adrift of the post-season places in the Eastern Conference with seven fixtures remaining, while the fourth-placed Timbers are seven points clear of Real Salt Lake in the battle for home-field advantage.
Elsewhere, 10-man Philadelphia Union were 3-0 winners over defending champions Columbus Crew, Toronto defeated Chicago Fire 3-1 and New York City drew 0-0 with Nashville, while the El Trafico derby between LA Galaxy and Los Angeles FC ended 1-1.
Seattle booked their spot in the second round of the play-offs thanks to goals from Jordan Morris, Nico Lodeiro and Raul Ruidiaz on Tuesday, earning a home date with Dallas.
Morris, Lodeiro and Ruidiaz all scored in the same MLS match for the fourth time, more than any other trio of team-mates since the start of the 2018 season, per Opta.
Lodeiro opened the scoring in the 18th minute – Morris teeing up the Uruguayan for a first-time shot past LAFC goalkeeper Pablo Sisniega.
LAFC's star captain Carlos Vela had a penalty saved three minutes later as Sounders goalkeeper Stefan Frei stopped a non-shoot-out spot-kick for the first time since April 2016, after allowing goals on the previous 18 on-target penalties he had faced.
After Morris and Lodeiro hit the woodwork in quick succession, Ruidiaz doubled the lead in the 66th minute before Eduard Atuesta reduced the deficit 11 minutes later.
Morris, though, restored Seattle's two-goal advantage within three minutes as the Sounders moved through to the next round.
Meanwhile, expansion franchise Nashville stunned Toronto 1-0 after extra time to earn an Eastern Conference semi-finals berth.
Daniel Rios' 108th-minute goal settled the contest in Connecticut, where seventh seeds Nashville became the third team in MLS history to win each of their first two play-off matches.
Rios' winner was also the first Toronto has ever conceded in extra time of a MLS play-off clash.
Nashville will now face Columbus Crew for a place in the Conference finals.
In the day's other fixture, New England Revolution shocked Eastern Conference top seeds Philadelphia Union 2-0.
First-half goals from Adam Buksa and Tajon Buchanan set the tone for the Revolution, who are the first team to score multiple goals in an away match against the Union all season.
Next up for Bruce Arena's Revolution are Orlando City.
Roldan struck in the 18th minute for the unbeaten Sounders, who left PayPal Park in San Jose with maximum points on Wednesday.
After the Earthquakes failed to clear their lines, Roldan riffled a thunderous half-volley into the back of the net from outside the penalty area.
The Sounders are now four points clear of the Earthquakes and LA Galaxy, who have played a match less in the west.
David Beckham's Inter Miami – coached by former Manchester United defender and midfielder Phil Neville – suffered a 2-0 defeat at home to Montreal following a 140-minute weather delay.
Bjorn Johnson scored twice in the space of 11 first-half minutes to give visitors Montreal a 2-0 lead inside the opening half an hour in Miami.
The match was then suspended in the 47th minute due to lightning strikes at DRV PNK Stadium, where Montreal held on for victory after more than two hours of waiting.
Montreal top the Eastern Conference, level on eight points with New England Revolution, who played out a 1-1 draw against Philadelphia Union, while Inter Miami have five points from five games.
Elsewhere, Toronto celebrated their first win of the season after topping defending champions Columbus Crew 2-0, Houston Dynamo were 1-0 victors over Sporting Kansas City, while Minnesota United defeated Vancouver Whitecaps by the same scoreline.
Johnny Russell's 79th-minute goal gave Sporting KC a 2-1 win away to Seattle Sounders, locking up a play-off spot for the second-placed team in the Western Conference table as Russell netted for the seventh straight game.
Colorado also are in after defeating Portland Timbers 2-0 behind golas from Dominique Badji and Diego Rubio.
The Seattle loss ensured New England, who face Orlando City on Sunday, will finish atop the overall table. The Revs are on 69 points, 20 points clear of Philadelphia and Nashville in the Eastern Conference and 11 clear of Seattle overall.
Nashville had a chance to clinch the play-offs with a win but fell 1-0 to Philadelphia Union on Kacper Przybylko's first-half penalty.
Inter Miami got a goal and three assists from Gonzalo Higuain, while his brother Federico also found the net in a 5-1 rout of Cincinnati, who lost their ninth in a row.
Toronto dealt a blow to rival Montreal's play-off hopes as Jozy Altidore's free kick in the fifth minute of stoppage time secured a 1-1 draw after Sunusi Ibrahim had netted in the 55th minute for the visitors.
Minnesota and LAFC also finished at 1-1, as did San Jose Earthquakes and Vancouver Whitecaps.
New York City crushed DC United 6-0 and Sean Nealis' 87th-minute goal lifted New York Red Bulls past Columbus Crew 2-1.
Sebastian Lletget's brilliant 83rd-minute equaliser gave LA Galaxy a 2-2 draw with Dallas, while Chicago Fire downed Real Salt Lake 1-0.
The victory brought the visitors within two points of the first-placed Sounders in the MLS Western Conference table, with one fewer match played.
KC captain Johnny Russell set the tone in the 31st minute with a beautiful free kick from just outside the area to give the visitors the lead, and Daniel Salloi doubled the advantage before half-time.
After Fredy Montero answered for Sounders in the 51st minute, Cameron Duke sneaked behind the defence in the 72nd minute to seal the win.
KC are unbeaten in their last five matches and have only one loss in their last 10.
A brace from Gustavo Bou helped New England Revolution expand their lead atop the Eastern Conference with a 2-1 win over Montreal.
Kacper Przybylko found the net for the third straight game, putting home a rebound in the 85th minute to salvage a 1-1 draw for Philadelphia against Inter Miami as Phil Neville's side remain bottom of the table.
New York City FC matched their season-high in goals, scoring four times after the break in a 5-0 demolition of Orlando City.
Ola Kamara's 27th-minute goal gave DC United a 1-0 victory over New York Red Bulls.
Sibling pair Diego and Yimmi Chara were among the goals as the Timbers – unbeaten in six matches – eased past RSL at Providence Park on Saturday.
Felipe Mora, Dairon Asprilla, Jaroslaw Niezgoda and Cristhian Paredes also scored for the Timbers, who have netted in 16 consecutive matches against RSL (including play-offs) – the second longest streak against any opponent in their history, behind the 17 straight versus Dallas from August 2012 to March 2018.
The Timbers led 2-1 at half-time before putting RSL to the sword in the second period to match their six-game unbeaten streak from September-October last season.
Portland are fourth in the Western Conference, six points behind leaders Sporting Kansas City, while RSL occupy the seventh and final play-off position in the west.
Los Angeles FC are three points outside the top seven following their 2-0 defeat to San Jose Earthquakes, while Vancouver Whitecaps are also on 33 points after topping Dallas 1-0.
The Union defeated Atlanta 1-0 thanks to Kacper Przybylko's goal with less than 20 minutes remaining.
Back-to-back wins sent Philadelphia up to fourth in the Eastern Conference as Atlanta's three-game winning streak came to an end to leave them eighth in the east and outside the post-season positions.
In other results, Supporters' Shield leaders New England Revolution were 2-1 winners over Orlando City.
The Revolution extended their MLS single-season record for wins by one-goal margins to 16. Nine of New England's last 10 MLS victories have come by a one-goal margin.
It continued Orlando's misery against New England – the team have never won at the Revolution (D1 L5), the only side they have visited more than three times without recording a victory in MLS play.
DC United prevailed 4-2 against FC Cincinnati, New York Red Bulls overcame rivals New York City 1-0, defending champions Columbus Crew won 2-1 against Montreal, Houston Dynamo lost 2-0 to Minnesota United, while Colorado Rapids and Toronto played out a 0-0 draw.
Patrick Mullins' first-half goal saw Toronto edge FC Cincinnati 1-0 on Sunday to book a spot in the play-offs.
Mullins produced a side-footed finish from inside the area after a Richie Laryea cutback just before the half-hour mark.
Toronto are top of the Eastern Conference and three points clear of Philadelphia Union.
Philadelphia won six straight home regular-season matches for the first time in their history, as per Opta, thanks to a 2-1 win over Montreal Impact.
Danny Musovski scored a double as LAFC enjoyed a 3-1 victory against Seattle Sounders.
LAFC are fourth in the Western Conference, which the Sounders top.
Erik Hurtado scored a spectacular volley to see Sporting Kansas City edge a 10-man Nashville 2-1.
Hurtado produced a wonderful finish from Amadou Dia's lofted pass to earn Sporting three points.
New England Revolution beat New York City 2-1, Chicago Fire were 2-1 winners over DC United and Jaroslaw Niezgoda netted twice as Portland Timbers claimed a 3-0 victory against San Jose Earthquakes.
Toronto moved level on points with Philadelphia after a 2-1 win over Inter Miami and the Union's 2-1 defeat to Columbus Crew on Sunday.
Columbus took a 37th-minute lead at home, Artur finding the bottom corner from 20 yards.
However, Philadelphia drew level in the 57th minute thanks to a penalty from Jamiro, although the hosts would strike late.
Krisztian Nemeth got on the end of a Luis Diaz Espinoza cross from the right to tap away a winner six minutes from time for Columbus, who are third in the Eastern Conference.
Toronto boosted their chances of winning the Supporters' Shield by overcoming Inter Miami.
Former Juventus midfielder Blaise Matuidi opened the scoring for Inter Miami with his first MLS goal.
But Toronto would win after conceding the opening goal for the third time this season, which is tied for the most with San Jose Earthquakes, as per Opta.
Ayo Akinola scored a fine equaliser after outmuscling his opponent before Gonzalo Higuain almost responded for Inter Miami, hitting the crossbar with a powerful 20-yard effort in the 79th minute.
Instead, Alejandro Pozuelo tucked away an 84th-minute penalty for the winner for Toronto.
Pozuelo has scored each of his past seven penalties for Toronto in MLS.
Valentin Castellanos scored a hat-trick to inspire New York City to a 5-2 derby win over the Red Bulls.
Castellanos became just the second player to net a hat-trick in the Hudson River Derby, joining David Villa (2017).
Elsewhere, Teal Bunbury's brace saw New England Revolution overcome DC United 4-3 in a thriller and Atlanta United beat Cincinnati 2-0.
Orlando City edged Montreal Impact 1-0, Colorado Rapids beat Seattle Sounders 3-1, the Portland Timbers overcame the Vancouver Whitecaps 1-0 and LA Galaxy edged Real Salt Lake 2-1.
Alejandro Pozuelo's fine run of form continued as Toronto came from behind to beat the Philadelphia Union 2-1 in Connecticut.
Sergio Santos' delicate chip had put Philadelphia ahead in the fifth minute, but Toronto fought back in the second half.
Ayo Akinola headed in a Tony Gallacher cross from the left approaching the hour-mark to bring Greg Vanney's side level.
Pozuelo scored what proved to be the winner in the 76th minute, heading in at the back post following a corner.
As Toronto won for the 10th time in their past 13 meetings with the Union, Pozuelo has been directly involved in 10 goals since the MLS regular season resumed in August, as per Opta.
Toronto joined Columbus on 31 points atop the Eastern Conference after the Crew were held to a 2-2 draw by Dallas.
LA Galaxy are bottom of the Western Conference after slumping to a 2-1 loss to the San Jose Earthquakes in the California Clasico.
The Galaxy seemed on track when Sebastian Lletget put away the opener after Javier Hernandez hit the post, and goalkeeper David Bingham saved Chris Wondolowski's 12th-minute penalty.
But Marcos Lopez drilled in a wonderful equaliser before half-time, and Andres Rios made no mistake with San Jose's second spot-kick of the game in the 82nd minute.
Orlando City continued their fine season with a 3-1 victory over the New York Red Bulls.
The club's tally of 29 points from their first 15 matches is five more than they have ever had through the same number of games in any previous campaign, according to Opta.
Gonzalo Higuain's Inter Miami fell to a 3-2 loss to New York City, while Atlanta United crushed DC United 4-0.
Montreal Impact and Chicago Fire drew 2-2, Alan Pulido scored a brace as Sporting Kansas City edged Houston Dynamo 2-1 and Minnesota United enjoyed a 2-0 victory over Cincinnati.
Western Conference leaders the Seattle Sounders beat the Vancouver Whitecaps 3-1, while the clash between the New England Revolution and Nashville finished goalless.
Goals from Kacper Przybylko and Sergio Santos in the opening 45 minutes helped the Union ease past the Timbers on Sunday.
Przybylko headed home the opener in the 26th minute and Santos doubled the lead five minutes later at Subaru Park, where he redirected his team-mate's shot.
VAR and a handball denied the Union a third goal, but Philadelphia made it 3-0 in the 63rd minute when Jack Elliott poked home to heap further misery on Portland.
The result snapped the Union's run of five consecutive defeats against the Timbers – Portland's four successive regular-season wins equalled Philadelphia's second longest losing streak at the hands of an opponent in regular-season play.
Philadelphia are second in the Eastern Conference – three points behind New England Revolution after eight games – while Portland are seventh in the Western Conference, nine points behind leaders Seattle.
The Sounders were forced to share the spoils against Austin but remain undefeated through eight rounds.
Seattle are off to the best start in their history and had lost just one of their eight home games against expansion sides heading into the Austin fixture.
The Sounders did find the back of the net via Fredy Montero with 15 minutes remaining, however a video review deemed Raul Ruidiaz was offside in the build-up.
Carlos Vela scored again but Los Angeles were forced to fight back three times to draw 3-3 with Philadelphia Union at the Banc of California Stadium.
Sergio Santos' 25-yard stunner put Philadelphia ahead before Vela curled a wonderful free-kick into the top corner.
Vela became the third quickest player to score 50 goals in MLS history, reaching the milestone in 61 games.
Jakob Glesnes' spectacular 40-yard free-kick restored Philadelphia's lead early in the second half, only for Diego Rossi to curl in a fine equaliser for Los Angeles.
After Brenden Aaronson again put the visitors ahead, Eddie Segura earned his side a point with a 71st-minute equaliser.
Los Angeles moved onto four points from their opening two games, while the draw got Philadelphia off the mark.
The Timbers handed Nashville SC a second straight loss with a 1-0 victory.
Diego Valeri's excellent first-half volley saw the Timbers claim their first win of the MLS season.
Romell Quioto had given Thierry Henry's Montreal an early lead at Red Bull Arena on Sunday, but his first-half red card proved costly.
Alejandro Bedoya levelled before Kacper Przybylko's brace either side of half-time, and Anthony Fontana sealed the win.
Quioto found the bottom corner with a 25-yard free-kick in just the fifth minute, but he was sent off 11 minutes later for elbowing Mark McKenzie.
Quioto's goal was the first time Montreal had scored from a direct free-kick shot since 2018, according to Opta.
Philadelphia quickly took advantage of the sending off as Bedoya drove home a powerful finish from inside the area to make it 1-1 midway through the first half.
Przybylko headed in Matt Real's cross on the stroke of half-time and the forward put away a Brenden Aaronson pass early in the second half.
Fontana's low 20-yard effort in the 65th minute sealed the win as Philadelphia returned to second, three points behind Columbus Crew, while Montreal are sixth.
As per Opta, Philadelphia have scored eight goals from outside the box this season, which is three more than any other MLS team.
The Union are without a win in their last six MLS fixtures, with their latest defeat coming at the hands of Charlotte FC in front of their home supporters last time out.
Curtin's side have managed just 20 points in their 19 league games after recording at least 32 at this stage in four of the previous five seasons.
And the Philadelphia head coach acknowledged his side's struggles in recent weeks, but highlighted the injuries within his squad as a major factor in their winless streak.
"The fingers are pointed at me first, and I accept that, and I take the responsibility for the current run that we are on," Curtin said.
"It hurts, but I still think the players are trying and giving everything that they can, but at the moment it is just not enough.
"We know that we're missing five to six key guys, and it hurts right now, and it's tough for us to catch a break and score a goal to make a play that changes the game."
Meanwhile, Montreal are enduring a losing streak of their own and are without a triumph since their 4-2 win over DC United back in May.
Laurent Courtois' side were beaten 4-1 by Colorado Rapids in their last MLS fixture, leaving them a point above bottom side Chicago Fire in the Eastern Conference.
L'Impact face a tough test should they want to return to winning ways this Sunday, having won one of their last nine meetings with the Union (D4 L4) dating back to October 2020.
PLAYERS TO WATCH
Montreal – Josef Martínez
Martinez has scored eight career goals against the Union in all competitions, having only scored more against Orlando (9).
However, Curtin’s side have managed to keep the Venezuelan at bay in recent meetings, having shut the striker out in each of the last four league meetings, with his last league goal against them coming back in 2019.
Philadelphia – Tai Baribo
In the absence of top scorer Julian Carranzo (10) and Daniel Gazdag (10), Baribo has the opportunity to take centre stage for the Union against Montreal.
The Israeli scored his first two goals for the club on his first start in their 4-3 defeat to Cincinnati, and will be looking to rediscover his goal-scoring touch at the Stade Saputo.
MATCH PREDICTION: PHILADELPHIA WIN
The Union come into the encounter as marginal favourites despite their six-game winless streak, but their impressive record against their opponents will give them some much-needed confidence.
Philadelphia have lost just one of their last nine meetings with Montreal (W4 D4), but that defeat came in the last meeting between the two sides, losing 3-2 back in March 2023.
Montreal have won just one of their last 14 matches in all competitions (D7 L6) dating back to mid-April. They are one of three MLS teams, along with the Union and St. Louis City SC, with only one victory in all competitions in that time.
OPTA WIN PROBABILITY
Montreal – 35.3%
Draw – 26%
Philadelphia – 38.7%
Inter required a 97th-minute equaliser from Christopher McVey to rescue a point, despite having led 3-2 entering the final 10 minutes thanks to a first-half Gonzalo Higuain hat-trick.
Brandon Vazquez scored twice to turn the game on its head, leaving Neville furious despite McVey's last-gasp intervention.
"We defended like little boys, we defended naively, we didn't compete, we lacked discipline and concentration," the former Manchester United and Everton defender said. "And that's unacceptable, unacceptable.
"Simple balls into the box we didn't deal with. Simple concentration bits we didn't deal with.
"We are in the stage of the season where concentration is the main thing, concentration will get you to win games of football, and it's not going to be easy; you've just got to defend and do the right things all the time, and defensively we were as poor as we have been all season."
Remarkably, it was not Saturday's first eight-goal draw, as Minnesota United and the Portland Timbers had earlier played out a thriller.
Sebastian Blanco got the scoring started in the first minute, but there was no late drama in this one, with all eight goals netted before the 70-minute mark.
This was the first time in MLS history two matches on the same day have seen both teams score at least four goals, but there was a chasm between the Philadelphia Union and the Houston Dynamo in Saturday's third high-scoring game.
The Union ran out 6-0 winners as Mikael Uhre continued his stunning run of form at Subaru Park, netting either side of half-time for his fifth and sixth goals in his past four home games.
Uhre had also scored twice in a 7-0 defeat of DC United earlier in July, making Philly the first team to win multiple games by a six-goal margin in a single MLS season.
Elsewhere, New York City FC lost ground on the Union in the East as they drew with CF Montreal, while Sebastian Druissi continued his MVP bid by inspiring Austin FC to a 2-0 win at Sporting Kansas City.
"He continues to demonstrate why he deserves that [award]," said Austin coach Josh Wolff.
A play-off place in MLS already secured, Philadelphia extended their unbeaten run to four games.
Andrew Farrell's own goal was followed by Anthony Fontana's strike and the Union moved within three points of Toronto despite Tajon Buchanan's 80th-minute effort for New England.
Farrell turned a cross into his own net to give Philadelphia the lead in the first half before Fontana lobbed New England goalkeeper Matt Turner following a Jamiro pass in the 69th minute.
Fontana has scored four of his eight MLS goals for Philadelphia against New England, as per Opta.
Buchanan produced a wonderful strike from 20 yards to give the Revolution hope, but Philadelphia held on.
The Revs went down 4-2 to New York Red Bulls last time out to make it four defeats in their last five games, and eight losses in 11 overall this season in MLS.
New England are bottom of the Eastern Conference, but Porter hopes lessons have been learned ahead of hosting Philadelphia on Saturday.
"Three of the four [goals NYRB scored] were individual mistakes that are easily correctable," Porter told The Blazing Musket. "We've gone to the training ground and corrected a few of those situation.
"But it's just individuals in those moments have to be better. It wasn't a bad team-defending performance, but three of the four goals we gave up were routine."
The Union have double the number of points compared to their opponents, having played one game more, as they occupy ninth place in the East.
The Us are themselves not in great form, though, as they lost 2-1 at home to New York City FC in their most recent game - a contest overshadowed by a raccoon that entered the field.
They have just two points from the past 18 on offer, meanwhile, and head coach Jim Curtin admits it is on him and his players to turn things around.
"The guys fight until the end, and we have to find a way to get out of this," Curtin said. "We're the only people that are going to get us out of it.
"The people in that locker room, the coaches, the players, they recognise that. They've shown they can beat anybody, and we're the only ones that can dig us out of this now."
PLAYERS TO WATCH
New England Revolution - Carles Gil
Gil got the Revs temporarily on level terms against New York Red Bulls, with that his 100th regular-season goal contribution in MLS. That makes the Revs' attacking midfielder the seventh European player to reach that milestone, and the second Spaniard after David Villa.
Philadelphia Union - Julian Carranza
Carranza was on target for the Union in their midweek loss to New York City, coming from one of nine attempts he had on target. The former Argentina age-grade international has now registered four-or-more shots in four MLS career matches.
To put that in perspective, the two other players to have done so in the club's history - Conor Casey and Andrew Wenger - have done so in a combined two games (one each).
MATCH PREDICTION: DRAW
Philadelphia have won 12 matches against the Revs across all MLS competitions, which includes MLS is Back, since 2018 - their best return against any single opponent across that period.
New England's tally of seven points from their opening 11 games is their worst-such return at this stage of a campaign in club history, with only two out of 17 teams in the post-shootout era (since 2000) managing to reach the playoffs from this position.
However, there is some hope for them this weekend as the Union's one point across their past five matches is their fewest across any five-game span within a single season since April 2017.
OPTA WIN PROBABILITY
New England Revolution - 36.1%
Draw - 28.8%
Philadelphia Union - 35.1%
The Union players had the names of black victims of police brutality on their shirts instead of their own, and captain Bedoya earned the team three points in the Group A clash.
The outcome left City without a win in three games overall this season, including two MLS games played in March, making it their worst start to a campaign.
The match kicked off at 09:00 local time (13:00 GMT) at the ESPN Wide World of Sports Complex in Florida to avoid the afternoon heat and potential thunderstorms.
After a dull first half without any dangerous openings, former United States international Bedoya got the better of Sean Johnson from the right side of the box in the 63rd minute after City failed to clear his initial cross.
Union's Kacper Przybylko had a goal correctly ruled out for offside four minutes later as the game finally came to life.
Andre Blake produced a fine save to prevent City striker Heber's effort from eight yards finding the bottom-right corner, before racing off his line to deny Gary Mackay-Steven when one-on-one in stoppage time.
City's wait for a first goal of 2020 consequently continued, while the Union secured their first clean sheet after conceding five across their two fixtures before the season's suspension in March amid the coronavirus pandemic.
