The Brooklyn Nets clinched a 4-1 series win over the Boston Celtics, while reigning champions the Los Angeles Lakers are on the brink of elimination.
The Lakers, without Anthony Davis, lost 115-85 to the Phoenix Suns and trail 3-2 in the best-of-seven series.
Elsewhere, the Denver Nuggets secured a 147-140 win in double-overtime against the Portland Trail Blazers.
The Blazers’ Damian Lillard scored 55 points including a play-off record 12 three-pointers in defeat.
James Harden scored a 34-point triple-double in the Nets’ 123-109 win, adding 10 rebounds and 10 assists.
Kyrie Irving added 25 points and Kevin Durant had 24 as the Nets shot 51.2 percent and made 15 of 32 three-point tries.
The Nets will play the Milwaukee Bucks in their first Eastern Conference semi-final since 2014.
Harden said: “It’s time to lock in now.
“We’ve dealt with so much adversity through the regular season, it felt good to get some meaningful games in.
“We’re a special group, especially when we lock in defensively. If we can get three or four stops in a row we can get it going offensively because we’ve got that much firepower.”
‘Win or go home’ for Lakers
LeBron James said the Lakers have got to be better if they want to force a game seven against the Suns.
The Lakers struggled without star forward Davis, who was ruled out with a left groin strain.
“A lot to cover and see what we can do better in game six, but they pretty much just kicked our ass, there’s nothing else really to say,” James said.
Devin Booker recorded 30 points, seven rebounds and five assists as the Suns won their second consecutive game in the series.
James hopes the high-stakes nature of Thursday’s game in Los Angeles will bring out the best in the reigning NBA champions.
“It’s literally win or go home at this point,” James said. “You shoot all the bullets you got and throw the gun too.
“I’m looking forward to the environment. Obviously the Laker faithful will give us a lot of energy. I look forward to the moment and the challenge, and see what brings out the best of me.”
Damian Lillard twice sent the Blazers to overtime as he recorded the first 55-point, 10-assist game in NBA play-off history.
But the Nuggets were ultimately too strong as they took a 3-2 series lead, with Nikola Jokic scoring 38 points, adding 11 rebounds and nine assists.
Monte Morris scored 28 points, Michael Porter Jr had 26 points and 12 rebounds, and Austin Rivers contributed 18 points and seven assists.