Superstars Devin Booker and Kevin Durant have scored 36 points apiece and Australian Jock Landale played a key role at both ends of the floor as Phoenix downed Denver 129-124 to level their NBA Western Conference semi-final series at 2-2.

The Suns won despite a monster 53-point game from Nuggets centre Nikola Jokic, who even ripped the ball away from Phoenix owner Mat Ishbia at one point after it went out of bounds, earning the Denver All-Star a technical foul.

But the combative Landale was able to shut down Jokic and fellow Denver big Aaron Gordon on several key plays, while also chipping in with eight points and five rebounds in 20:37 of game-time.

The series returns to Denver for Game 5 on Tuesday (Wednesday AEST).

The Suns took a 98-92 lead into the fourth quarter after a scoring flurry from Booker, who had 17 points in the third. Phoenix wouldn't trail in the fourth, although Denver didn't go quietly.

The Nuggets were down 116-106 with 4:55 remaining but never panicked, slowly cutting into the lead.

They pulled within 123-120 with 22.4 seconds left but TJ Warren made two free throws to push the margin back to five.

Booker - averaging 36 points on 60 per cent shooting in these playoffs - was hot once again, shooting 14 of 18 from the field, including 3 of 4 on 3-pointers. Bench guard Landry Shamet finished with 19 points, shooting 5 of 8 on 3s.

Jamal Murray added 28 points and seven assists for the Nuggets.

Suns point guard Chris Paul missed his second straight match with a strained left groin suffered during Game 2.

In Philadelphia, James Harden hit the go-ahead 3-pointer with 18 seconds left in overtime and scored 42 points to help the 76ers stave off a wild Boston Celtics comeback in a 116-115 victory that evened their series 2-2.

"I just want to win," said Harden, who also hit the floater with 16 seconds left in regulation to send the game into OT.

"Today was do-or-die for us."

The Sixers were on the brink of defeat numerous times over the final 17 minutes, no more so than when Joel Embiid crashed into Smart on a driving, one-handed bank shot with 1:49 left but was whistled for an offensive foul.

The play was reviewed and the call stood. Boston kept its 112-111 lead with 1:49 left in OT.

Embiid, the NBA MVP, kept his composure and eventually got to the line to sink two free throws with 59 seconds left. He finished with 34 points and 13 rebounds. Harden added nine assists and eight rebounds.

Jayson Tatum struggled to score early but finished with 24 points, 18 rebounds, six assists and four blocks for Boston.

Jaylen Brown scored 23 points and Marcus Smart had 21.