Harden, Kevin Durant and Kyrie Irving will lead the second-seeded Nets in an Eastern Conference semi-final showdown with Giannis Antetokounmpo and third seeds the Bucks, starting Saturday.
Brooklyn's 'big three' have the Nets as favourites to win their maiden championship in a playoff campaign also featuring the Philadelphia 76ers and Utah Jazz.
Harden joined the Nets from the Houston Rockets via a blockbuster trade in January, with the former MVP's eyes on a much-coveted title.
During his time in Houston, Harden reached two Western Conference Finals as the franchise never advanced to the showpiece – Stephen Curry and the Golden State Warriors often standing in the way, while LeBron James and the Los Angeles Lakers also thwarted the Rockets in the semi-finals last season.
Now, Harden senses his best opportunity to add an NBA ring to his list of league honours.
"I ran into some very, very good teams which is one of the reasons I've been short [of winning a title]," Harden told reporters via a Zoom call on Friday.
"[But] you look at our roster, we're elite too. It's going to be a showdown but I'm more than confident going into this postseason just because of the roster and our schemes and the things that we can control and the versatility that we have."
Harden added: "Obviously, there's only a handful of teams that have an opportunity. And we're one of those teams this year.
"So, the excitement is there, but I think just the focus is the most important thing for myself. And just trying to rub that focus level and that engagement to detail into every one of my team-mates."
The Nets saw off the Boston Celtics 4-1 in the opening round but will face a stiffer test against two-time reigning MVP Antetokounmpo and his Milwaukee support cast, including Jrue Holiday.
With Brooklyn's Jeff Green ruled out of Game 1, Nets head coach Steve Nash said: "I think the strategy we'll probably start with is probably similar from a team-defending standpoint.
"It's also the type of thing we have to work our way through as the series goes on and have a better feel for it, have more and more of an understanding collectively, and also be able to adjust and adapt within our schemes, not just change our schemes. The team concepts will be the same regardless."
Harden had initially been ruled out of Game 5 against the Milwaukee Bucks in the Eastern Conference semifinals.
The former Houston Rockets star has been managing a hamstring injury since the start of April.
Harden, who had been making an MVP run prior to the initial setback, returned in the closing stages of the regular season.
He then averaged 27.8 points per game in the first-round series against the Boston Celtics but bowed out 43 seconds into Game 1 at home to the Bucks.
The potential for Harden to feature in Game 5 lifts the Nets, who have also now lost Kyrie Irving to an ankle issue.
Having gone 2-0 up against Milwaukee without Harden, Brooklyn lost both games on the road to level the series.
Kevin Durant has led the team with 29.8 points per game in the series but was limited to nine-of-25 shooting in Game 4.
Young fuelled Wednesday's 116-113 win away to the Bucks in Milwaukee, dominating with a game-high 48 points along with 11 assists and seven rebounds as the Hawks drew first blood.
Atlanta's run has been improbable, having sacked their head coach Lloyd Pierce in March at 14-20, before storming into the NBA playoffs under interim Nate McMillan.
The Hawks have eliminated the fourth-ranked New York Knicks and top seeds the Philadelphia 76ers en route to their first Conference Final since 2015.
Young shook his head emphatically and responded with a clear "no" when asked if there was any ceiling on this Hawks side.
"I've been getting asked that a lot at the beginning of the season and I told everybody then, 'I didn't believe we had any ceiling, we can go as far as we want to'," Young told the news conference.
"I don't think there is a ceiling unless you put the finals on it. I believe in this team and we all believe in each other.
"It's definitely unique. It's one of my favourite teams I've been a part of it. It's special. It's definitely a unique group."
The Hawks have won Game 1 in all their postseason series and Young insisted there was a high level of belief within the Atlanta group which came from McMillan and the leaders.
"It really just comes from the leaders," he said. "The leaders from Nate down just believe.
"We have a group that believes in each other and is fighting for each other. Anything can happen. Our team believes that."
Young tied LeBron James (2007) and Hall of Famer Kobe Bryant (2001) for the most points scored in a playoff game in NBA history before turning 23 years old.
The 2020 All-Star (22 years and 277 days) is also the second youngest player in league history to record 45-plus points and 10-plus assists in a postseason game, with Luka Doncic (22 years and 98 days) the youngest to do so.
Young's 48 points are also the third most scored in a playoff game in Hawks history, behind only Bob Pettit (50 in 1958) and Dominique Wilkins (50 in 1986).
"I'm all for the biggest moments," Young said afterwards.
The point guard sprained his right ankle late in the third quarter when he stepped on referee Sean Wright's foot in Game 3 at State Farm Arena.
Young hobbled off and was taken to the locker room to get his injury assessed, but was able to return to the court early in the fourth quarter.
The 22-year-old's movement was restricted when he was returned and he will undergo a scan on Monday after doing damage in a game he finished with 35 points - a tally only bettered by Khris Middleton.
Young said following the defeat: "It's sore right now. It's hurting, it's frustrating. It's hurting a little bit and it's sore.
"I got some treatment on it. I'm going to go get some more in the morning. That's all I can do right now, is to get treatment."
Young said he had not spotted official Wright, who was out of bounds when he stepped on him.
"I didn't see him. I guess I’ve got to have eyes in the back of my head now to see who's behind me," he added.
Hawks coach Nate McMillan withdrew Young with a minute to go and is unsure if he will be able to call upon such a key man in Game 4 on Tuesday.
"I don't know right now," McMillan said when asked if Young will be fit. "When he returned to the floor, he was obviously limping on that [ankle]. When I subbed for him, we just decided to keep him out."
Giannis Antetokounmpo posted 33 points and 11 rebounds and Middleton put up a game-high 38 points and 11 rebounds for the third-seeded Bucks.
Young hurt his foot in the third quarter of Sunday's 113-102 defeat as the Milwaukee Bucks claimed a 2-1 series lead in the NBA playoffs.
Hawks guard Young suffered the freak injury when he stepped on referee Sean Wright's foot in Game 3 at State Farm Arena.
Young hobbled off and was taken to the locker room to get his injury assessed, but was able to return to the court early in the fourth quarter.
The 22-year-old was able to post 35 points in a losing effort at home to the third-seeded Bucks, who were fuelled by Khris Middleton and Giannis Antetokounmpo.
Atlanta had been 15-0 this season (regular and playoffs) when Young scored 35-plus points before Sunday as he had a team-high 35 points on 12-of-23 shooting. It was his eighth 30-point game this postseason, second most in a single playoff in team history (Bob Pettit, nine in 1963).
Young began the series last week by scoring 48 points and 11 assists as the Hawks took Game 1 in Milwaukee.
He tied Los Angeles Lakers superstar LeBron James (2007) and Hall of Famer Kobe Bryant (2001) for the most points scored in a playoff game in NBA history before turning 23 years old.
The 2020 All-Star (22 years and 277 days) also became the second youngest player in league history to record 45-plus points and 10-plus assists in a postseason game, with Luka Doncic (22 years and 98 days) the youngest to do so.
Young's 48 points were also the third most scored in a playoff game in Hawks history, behind only Bob Pettit (50 in 1958) and Dominique Wilkins (50 in 1986).
In Game 2, Young was held to 15 points but bounced back with 35 in the third game, going six for 14 from three-point range, taking his points per game for the week to 32.67, way up on his already impressive average of 25.3 from the regular season.
Young already sat out Tuesday's Game 4 win over the Milwaukee Bucks and he remains sidelined for Thursday's showdown with the NBA playoff series tied at 2-2, the Hawks confirmed prior to tip-off.
Atlanta's Young hurt his foot in the third quarter of Sunday's 113-102 defeat to the Bucks, suffering the freak injury when he stepped on referee Sean Wright's foot in Game 3 at State Farm Arena.
The Hawks' 110-88 win in Game 4 was the first game of this postseason in which no player on either team had 25-plus points, 10-plus rebounds or 10-plus assists, according to Stats Perform.
Milwaukee had just four points off turnovers, their fewest in any game over the last two seasons (regular season or postseason).
Atlanta's Game 4 victory was their largest playoff win since a 110-83 victory over the Boston Celtics in the 2016 first round. It was the franchise's first win by 20-plus points in the conference/division finals since the St Louis Hawks' 123-95 win over the San Francisco Warriors in the 1964 West Division Finals.
Young hurt his ankle in the third quarter of Sunday's 113-102 defeat as the Milwaukee Bucks claimed a 2-1 series lead in the NBA playoffs.
Hawks guard Young suffered the freak injury when he stepped on referee Sean Wright's foot in Game 3 at State Farm Arena.
Young hobbled off and was taken to the locker room to get his injury assessed, but was able to return to the court early in the fourth quarter.
The 22-year-old was able to post 35 points in a losing effort at home to the third-seeded Bucks, who were fuelled by Khris Middleton and Giannis Antetokounmpo.
He began the series last week by scoring 48 points and 11 assists as the Hawks took Game 1 in Milwaukee.
Young tied Los Angeles Lakers superstar LeBron James (2007) and Hall of Famer Kobe Bryant (2001) for the most points scored in a playoff game in NBA history before turning 23 years old.
The 2020 All-Star (22 years and 277 days) also became the second youngest player in league history to record 45-plus points and 10-plus assists in a postseason game, with Luka Doncic (22 years and 98 days) the youngest to do so.
Young's 48 points were also the third most scored in a playoff game in Hawks history, behind only Bob Pettit (50 in 1958) and Dominique Wilkins (50 in 1986).
In Game 2, Young was held to 15 points but bounced back with 35 in the third game, going six for 14 from three-point range, taking his points per game for the week to 32.67, way up on his already impressive average of 25.3 from the regular season.
Antetokounmpo led the way as the Bucks routed the Heat 132-98 on Monday for a commanding 2-0 lead in the first-round series.
Two-time reigning MVP Antetokounmpo posted 31 points in 31 minutes, while also tallying 13 rebounds, six assists and three steals on home court in Milwaukee.
A superstar with the basketball, Antetokounmpo also demonstrated his football skills after juggling the ball during a break in play against the Heat.
Afterwards, Greece international Antetokounmpo told reporters: "I can do probably like 300 of those.
"I used to play soccer when I was young. My dad used to be a soccer player. I love soccer.
"I wanted to play soccer. I didn't want to play basketball growing up."
Milwaukee – seeded third in the east – used a 46-20 opening quarter to crush Miami in Game 2 of their NBA playoff clash.
Jrue Holiday (11 points and 15 assists) added a double-double of his own, while Bucks team-mate Bryn Forbes made six three-pointers to contribute 22 points off the bench.
The Bucks set a franchise record for threes made in a playoff game after nailing 22 from beyond the arc.
Forbes, who joined the Bucks in November following four seasons with the San Antonio Spurs, said: "That was a huge part in me coming here. You know that there would be these opportunities and we would be in the playoffs.... It's just great to be in this position, be in the playoffs again and have an opportunity and stage."
"It's just how the game goes," Forbes added. "It's ebbs and flows. Some games you're open a lot more. Some games you aren't. Tonight I think we moved the ball great and had a lot of open shots."
Bucks star Holiday hailed Forbes, saying: "If my man got the hot hand, I'm going to him. And he wasn't missing, so at that point we were running everything to him just to -- really just to see what happens."
It was an impressive shooting display from the Bucks as head coach Mike Budenholzer added: "Guys have got to shoot it with confidence. They've got to let it fly. They've got to know they’re going to get threes.
"I think the activity offensively, the attack, can create good looks for us. We've just got to continue to let it fly when you're open."
"Lots of times, there's just so much talent in the league and so many good teams, sometimes you get the early lead and things just happen and it becomes a close game," Budenholzer said. "Today we were able to keep the focus."
The Bucks escaped with an 86-83 victory in Game 3 in the Eastern Conference semi-finals, with the Nets still leading the series 2-1.
Milwaukee had surrendered a 21-point lead before Jrue Holiday put the home team ahead for good with 11.4 seconds remaining.
Kevin Durant's 30 points and 11 rebounds were not enough for the Nets, who were again without injured superstar James Harden (hamstring).
Irving, however, was not too downbeat as he was able to appreciate the contest as a spectacle.
"Shoot, man, they did what they were supposed to do: come out aggressive, backs against the wall, and we had to weather that storm," he said.
"So that definitely kind of put us on our heels for the rest of the game, just playing catch-up, playing their style of basketball, and then they made some big timely shots which carried them forward.
"But we had our chances down the stretch. It was a possession-by-possession game. Both teams battling. So that's a good old-fashioned playoff game right there."
Durant highlighted how fine margins determined the outcome of a game that could have gone either way.
He said: "They played more physical, they were there at the rim and they just played their regular way, the way they've been playing the whole season.
"I think we got great looks, we need to knock them down, but they also did a good job of contesting and being physical and blocking shots at the rim.
"But for the most part we got back into the game, had plays down the stretch and they just ended up making a couple more shots."
Milwaukee made light of two-time MVP Giannis Antetokounmpo's absence with a hyperextended knee by beating the Atlanta Hawks 123-112 in Game 5 of the Eastern Conference Finals.
It gives the Bucks a 3-2 lead and leaves them one victory away from a shot at their first championship since 1971.
Portis joined Milwaukee last offseason and has quickly established an affinity with a fanbase who chanted his name raucously as he racked up 22 points in 36 minutes on Thursday.
"Milwaukee's a tough city. We were meeting with some people at the start of the season in January and February," Portis told reporters afterwards. "They were telling us about the city, how tough it is to live here and things like that.
"The city goes through a lot. When they see someone who works hard and gives his all… it's a blue-collar city and I'm a blue-collar player.
"When I'm making shots, whether they're going in or not, I still give my all to the team, give 100 per cent for the name on the front of the jersey.
"They love players like that and it's just fun to go out and play this game with home court advantage and get them involved.
"Giannis went down and we had to step up. I didn't play the last couple of games. I kept working and knew my time was going to come. If you do things the right way, things always come around."
There were no shortage of players stepping up in the required fashion.
Brook Lopez amassed a playoff career-high 33 points for the third-seeded Bucks, while Khris Middleton weighed in with 26 points, 13 rebounds and eight assists.
Jrue Holiday also managed a double-double of 25 points and 13 rebounds, and former Chicago Bulls and Washington Wizards forward Portis is delighted to be in such company after being released by the New York Knicks.
"Coming here was the best decision of my career," he said. "Having good veterans like Giannis and Brook to coach me up on how to be a two-way player.
"Guys like Khris and Jrue, who are unselfish and put the ball in hole for me to shoot my shots. And having coaches like coach Bud [Mike Budenholzer] and all the coaching staff who believe in me."
Portis added: "I've finally found peace. I'm at peace with my life, at peace with myself and everything around me.
"The pandemic helped me find out more about myself. Being at home for nine or 10 months straight, watching guys on TV play in the bubble and not being able to go there really hurt. But I got a chance to really work on my game and that helped me prepare for the moment."
Injuries crippled the Lakers for most of the season as they slipped down to the play-in tournament and the seventh seed, but Anthony Davis and LeBron James starred at Staples Center on Thursday.
Davis posted a dominant double-double of 34 points and 11 rebounds and James put up 21 points as the Lakers claimed a 2-1 series lead following back-to-back victories against the second seeds in the playoffs.
Giannis Antetokounmpo and the Milwaukee Bucks, meanwhile, are poised to sweep the Miami Heat after easing to a 113-84 win.
Bucks superstar Antetokounmpo posted 17 points and 17 rebounds to go with five assists, while Khris Middleton (team-high 22 points) and Jrue Holiday (19 points and 12 assists) contributed en route to a commanding 3-0 series lead.
The Bucks – who are eyeing their first championship since 1971 – can seal a sweep on Saturday.
Jokic inspires Nuggets
MVP frontrunner Nikola Jokic was at his brilliant best as the Denver Nuggets outlasted the Portland Trail Blazers 120-115 on the road. Jokic scored 36 points and collected 10 rebounds to guide the third-seeded Nuggets to a 2-1 series lead in the west. Damian Lillard's 37 points and Jusuf Nurkic's 13-point, 13-rebound double-double were not enough for the Trail Blazers.
Milwaukee's Holiday produced another impressive display against the Heat following his 15-assist performance in Game 2 as he became the first Bucks player with back-to-back 10-plus assist games in the playoffs since Sam Cassell in 2001. The 2013 All-Star was plus-37 in Game 2 and plus-42 in Game 3. According to Stats Perform, Holiday became the first NBA player to have a plus-minus of plus-37 or better in back-to-back games since Kobe Bryant in 2003.
Miami's shooting woes
The less said about the Heat's shooting on Thursday, the better. As a team, Miami were just 37.6 per cent from the field – making 32 of their 85 shots. From three-point range, the Heat were only 28.1 per cent (nine of 32). Goran Dragic (eight points) finished three-for-14 shooting in 29 minutes, while Duncan Robinson (two points) was one of six from the field, having missed all four three-pointers.
Chris Paul and Devin Booker were not at their usual high standards for the Suns. Paul, who hurt his shoulder in Game 2, was three-for-eight shooting for just seven points. All-Star team-mate Booker had 19 points, but it was on six-for-19 shooting from the field in 41 minutes. He only made one of four attempts from beyond the arc.
Rivers lights up fourth quarter
Denver's Austin Rivers was in red-hot form in the final period against the Blazers. Rivers scored 16 of his 21 points in the fourth to help the Nuggets to victory.
Thursday's results
Los Angeles Lakers 109-95 Phoenix Suns
Milwaukee Bucks 113-84 Miami Heat
Denver Nuggets 120-115 Portland Trail Blazers
Nets at Celtics
The star-studded Brooklyn Nets visit the Boston Celtics on Friday, leading the Eastern Conference first-round series 2-0.
Bucks forward Middleton top-scored with an NBA playoff career-high 38 points, including five-from-eight three-pointers, and had 10 rebounds, five assists and five steals, as Milwaukee levelled the series at 3-3.
Two-time MVP Antetokounmpo produced a more aggressive display inside the paint to stay alive in the playoffs, putting up 30 points and 17 rebounds in a double-double display at home to the Nets.
Antetokounmpo played a key role in 14-0 fourth-quarter run, including a strong offensive rebound and slam, which warded off Brooklyn's threat.
Milwaukee's Antetokounmpo did not attempt one three-point shot in a clear change of strategy after criticism for his shooting earlier in the series.
James Harden started again for the Nets after returning from a hamstring injury in Game 5, getting through 39 minutes but was visibly hampered, lacking power and finishing with 16 points, five rebounds and seven assists.
Kevin Durant had another busy shift, playing 40 of the 48 minutes, however he could not carry the second-seeded Nets, scoring 32 points with 11 rebounds following his monster triple-double last time out.
PJ Tucker and Jrue Holiday were strong defensively, with the latter having four steals, harassing Durant – who only shot at 50 per cent from the field and two-from-eight beyond the arc.
Milwaukee led 59-48 at half-time with Antetokounmpo having 18 points in the opening half, shooting eight of nine from the field.
The Nets rallied in the third quarter and put pressure on the Bucks early in the last period with a 10-0 run.
Milwaukee hit back with their 14-0 run which led to Brooklyn benching Durant and Harden late.
The Nets will welcome the Bucks to Brooklyn for Game 7 on Saturday.
76ers at Hawks
The east and west's top seeds – the Philadelphia 76ers and Utah Jazz – could be eliminated on Friday, with the Atlanta Hawks and the Los Angeles Clippers both looking to wrap up their Conference semi-final series on their home courts leading 3-2.
After scoring just five points in the first half, Middleton out-scored the entire Hawks team 13-0 over a two-minute span early in the second half on the way to a 23-point third period and 32 points in the game.
With Giannis Antetokounmpo missing another game thanks to a hyperextended left knee, it was Middleton who stepped up and led Milwaukee to their first NBA Finals since 1974.
"Khris caught a streak there in the third quarter, and particularly coming out to start it," Bucks head coach Mike Budenholzer told reporters. "So I think that was the turning point in the game."
Though Middleton had a couple of poor shooting games in the Hawks series and was not in the offensive flow in the first half Saturday, his coach had no doubt he would come through eventually.
"You know, he's a bucket-getter," Budenholzer said. "He's just got such a great overall package, and I think he's just an underrated playmaker. He's an underrated passer.
"But it's all built off him just being a great, great shooter. So any time he can shoot, I think he's got the ultimate green light. He can pass it, he can shoot it, he can do a little bit of everything.
"I love the way he competes and he's there. You know, he's been special. We'll need more of that going forward."
Regardless of Antetokounmpo's status going forward, Middleton will be a key factor in the NBA Finals against the Phoenix Suns.
For a player who has experienced one disappointment after another in his first few seasons with the team, getting over the hump on Saturday was something special.
"It's been a long journey but it's been a great journey - it's been worth it," Middleton said. "We put ourselves in position to win the NBA Finals after winning 15 games in our first year here.
"Several years not making the playoffs to the last two years thinking we had a chance and we just didn't do enough, and now we're here.
"It's what we worked for, and I'm extremely happy that we're still playing."
Though the Bucks had some margin for error with a 3-2 series lead entering Saturday's game, it was Middleton who took the lead in ensuring they did not need to use that cushion, and his team-mates were grateful.
"At the end of the day, Khris carried us," Jrue Holiday told reporters. "He put us on his shoulders. I'm riding with him right to the Finals.
“Khris is the heart of this team and Giannis is the soul of this team and without them, we really wouldn’t be here."
After going off for 45 points in the opener, All-Star Mitchell posted 37 points to lead the Jazz to a 117-111 victory at home to the Clippers in Game 2 in the NBA playoffs on Thursday.
Mitchell was supported by fellow All-Star and newly crowned Defensive Player of the Year Rudy Gobert, who put up 13 points, 20 rebounds, three blocks and two steals in Utah.
Utah's Mitchell is averaging 28.4 points in his playoff career, only behind LeBron James (28.7), Jerry West (29.1), Kevin Durant (29.2), Allen Iverson (29.7) and Michael Jordan (33.4).
The in-form Jazz extended their winning streak to six games – the team's longest unbeaten run in the playoffs since celebrating seven consecutive victories in 1998.
Kawhi Leonard and the fourth-ranked Clippers were looking to even the series by splitting Utah's homestand, but the visitors fell short in Game 2.
Reggie Jackson had a team-best 29 points on 11-for-19 shooting as Paul George (27 points and 10 rebounds) and Leonard (21 points) contributed.
In the Eastern Conference semi-finals, the Milwaukee Bucks escaped with an 86-83 victory against the Brooklyn Nets in Game 3.
The Bucks had their backs against the wall after falling into a 2-0 hole against the second-seeded Nets, but responded on home court in Milwaukee.
Milwaukee surrendered a 21-point lead at home to the Nets before Jrue Holiday put the Bucks ahead for good with 11.4 seconds remaining.
Giannis Antetokounmpo posted 33 points and 14 rebounds, while Khris Middleton top-scored with 35 points and 15 rebounds as Kevin Durant's buzzer-beating three-point attempt for the Nets bounced off the rim.
The Bucks are the only NBA team in the last 15 years to have two players (Antetokounmpo and Middleton) score 15-plus points in a quarter with no other team-mates posting a point (regular season or postseason), according to Stats Perform.
Antetokounmpo and Middleton combined for 68 points and 29 rebounds. Per Stats Perform, they are the first duo to combine for those numbers in a playoff game since Shaquille O'Neal and Kobe Bryant in 2001.
Durant's 30 points and 11 rebounds were not enough for the Nets, who were again without injured superstar James Harden (hamstring).
76ers at Hawks
The top-seeded Philadelphia 76ers will visit the Atlanta Hawks in Game 3 of their Eastern Conference semi-final matchup on Friday. The series is level at 1-1.
Durant produced a masterclass in Game 5 at Barclays Center on Tuesday; scoring 49 points, claiming 17 rebounds and providing 10 assists as the Nets took a 3-2 series lead.
The two-time NBA champion became the first player to put up at least 45 points, 15 boards and 10 assists in a postseason game.
Durant stole the show as James Harden struggled on his return from a hamstring injury for a Nets side missing Kyrie Irving due to a sprained ankle.
Nets coach Nash said of the 2017 and 2018 NBA Finals MVP: "It's ridiculous what he's able to do.
"We knew he was capable of nights like this, but to do it tonight… We miss Ky, James obviously is soldiering through his ailments. We're down bodies, we're wounded. And for him to have the toughness, the mentality. That's what makes him one of the all-time greats.
"This is a performance that's a signature performance for Kevin, and it was beautiful to watch."
Durant is focused on trying to repeat his incredible exploits as the Nets go in search of NBA glory.
He said: "I didn't even think about anything but just each possession. I was trying to win each possession, and I didn't think about how many points I had or shot attempts or rebounds or assists.
"That's the approach I always take, and I was able to rack up some points. I did play every minute, so that did help with my point total."
Asked how he ranked his performance, he said: "Once they happen, I just move on and see if I can do it again. That was a fun game to be a part of, but there have been a lot of games in my career I feel have been just as fun."
Giannis Antetokounmpo scored 34 points and took 12 assists but the Bucks lost despite moving into a 17-point lead in the third quarter.
Irving sprained his right ankle in the Nets' 107-96 loss in Game 4 on Sunday and underwent an MRI which confirmed he would not be available for Tuesday's clash, with the NBA playoff series in tied at 2-2.
Nets guard Irving joins former MVP Harden on the sidelines, with the latter still absence because of a hamstring he re-injured in Game 1.
Brooklyn head coach Steve Nash said the length of Irving's absence remains unknown.
"I have to wait and see how it progresses, I think," Nash said.
"And then the experts would have to wait and see how it progresses and give you a clearer picture on what the window would be for his return."
Nash added that Harden was "working out right now" but was unclear on his return to play timeframe.
The second-seeded Nets – eyeing their maiden championship – have battled injuries throughout the 2020-21 campaign, with Harden missing 21 games late in the regular season due to his troublesome hamstring.
"It's tough to lose great players but we've lost guys all season," Nash said. "If there's any silver linings, it's that we've continued to win games regardless of who's been available.
"We've been able to adapt on the fly which is difficult to do sometimes. That's something we have some experience with. We should have some comfort and belief."
The absence of two-thirds of the 'Big Three' puts a heavy burden on Kevin Durant, although Nash insisted it was not just about him.
"This does not fall on Kevin, this falls on the Nets," Nash said. "We've got to find a way together to play great basketball on both ends of the floor. We've proven we can do it.
"We try to stick to our principles and fundamentals, which is connectivity, competitive spirit, embracing the opportunity and playing together as a team."
Harden was initially ruled out alongside fellow All-Star Kyrie Irving (ankle) due to his troublesome hamstring, which had him sidelined after bowing out 43 seconds into the opening clash with the Bucks.
But Harden's status was upgraded to doubtful and then questionable on Tuesday, before being cleared to play less than an hour prior to tip-off at Barclays Center, where the series is tied at 2-2.
"I'm not sure the level of risk," Nets head coach Steve Nash said before the game. "I think it is James' decision. He wants to play. Ultimately, he wants to play. He's been pushing."
Harden – averaging 23.2 points, a postseason career-high 8.8 assists and 6.2 rebounds in the playoffs in 2020-21 – has been managing a hamstring injury since the start of April.
The former Houston Rockets guard, who had been making an MVP run prior to the initial setback, returned in the closing stages of the regular season.
Harden then averaged 27.8 points per game in the first-round series against the Boston Celtics but suffered an injury in Game 1 at home to Giannis Antetokounmpo's Bucks.
Having gone 2-0 up against Milwaukee without Harden, second-seeded Brooklyn lost both games on the road to level the series.
The Nets have won three of four Game 5's at home in best-of-seven series all-time after being tied 2-2. Their only such loss came in the 2003 NBA Finals against the San Antonio Spurs (93-83).
Brooklyn are outscoring opponents by 8.7 points per 100 possessions when both Harden and Irving are on the court this season (regular and postseason). That differential drops to plus-2.8 when neither is in the game.
Irving has been sidelined since spraining his right ankle in the Nets' Game 4 loss, missing Game 5 and 6 in the NBA playoffs.
With the second-round series set to be decided in Brooklyn on Saturday, the second-seeded Nets will be without Irving.
"Kai is still getting treatment... he's got some miles to make up, but progressing and sticking to his rehab," Nash said. "He is officially out."
Kevin Durant has been carrying the load for the Nets, with fellow MVP winner James Harden far from his best since returning from a hamstring injury in Game 5.
"If we're able to advance, I think he'll [Irving] be back at some point," Nash said. "So I don't know if that's in a few days, in a week or beyond, but it's not a season-threatening situation."
Irving has been averaging 26.9 points, 6.0 assists and 4.8 rebounds in 2020-21, while boasting career highs in field-goal percentage (50.6) and free-throw percentage (92.2).
In this season's playoffs, Irving is averaging 22.7 points, a career-best 5.8 rebounds and 3.4 assists for the Nets, who are eyeing their first NBA championship.
Harden left the court after only 43 seconds after re-injuring his right hamstring, but Kevin Durant and Kyrie Irving stepped up in his absence, along with Blake Griffin who had a throwback game.
Durant finished with 29 points, 10 rebounds and two blocks while Irving had 25 points and eight assists including 20 points in the first half but it was a collective effort on both defense and offense for the Nets.
Griffin made four three-pointers, totalling 18 points and 14 rebounds, the latter being a season-high for him since joining the Nets.
In contrast, the Bucks struggled from beyond the arc, shooting six from 30 with the main culprits being Jrue Holiday with two from seven and Khris Middleton who shot none from five.
At one stage in the first half, Milwaukee missed 11 consecutive three-point attempts to leave them playing catch up.
Giannis Antetokounmpo was the Bucks' best with 34 points, 11 rebounds, two blocks and four assists.
The Nets edged ahead in the first half where the Bucks rallied to finish the second quarter with a 14-3 stretch to trail by two points at the long break.
But Durant lifted Brooklyn in the third quarter, as the Nets piled on 35 points to open up a sizeable 14-point lead at the final change.
While the Bucks struggled from range, the Nets shot 15 from 40 beyond the arc, going at 37.5 per cent led by Joe Harris who made five from nine.
The series continues on Monday at Brooklyn's Barclays Center although the Nets will be sweating on Harden's status.
Nets superstar Harden hurt his hamstring during Saturday's 115-107 win over the Bucks in the NBA playoffs.
Harden lasted just 43 seconds after re-injuring the same hamstring which sidelined the former MVP for 21 of the final 23 regular-season games.
The second-seeded Nets will be without Harden for Monday's second showdown at Barclays Center in Brooklyn.
"James Harden has been diagnosed with right hamstring tightness," the Nets said via Twitter on Sunday.
"He is listed as out for Game 2 of the Eastern Conference semi-finals vs. Milwaukee. Further updates will be issued as appropriate."
As the star-studded Nets gear up for Game 2 in pursuit of a maiden championship, head coach Steve Nash told reporters: "He [Harden] has high hopes and he wants to be back ASAP. Now, I think we want to protect James, too. We want to make sure he's right.
"This is playoff time. This is time to take some risks, but it has to be right to take those risks -- we're not going to take any old risk. So, we hope he's back.
"He believes he can be back. But, we've got to see what happens and only can time can tell how he responds."
In this season's playoffs, Harden has been averaging 23.2 points, a career-high 8.8 assists and 6.2 rebounds through six games.
He has also been boasting postseason career highs in field-goal percentage (55.6) and three-point percentage (47.5).
