Julius Randle of the Knicks stretches after an injury during the...

Julius Randle of the Knicks stretches after an injury during the second quarter against the Heat at Madison Square Garden on Wednesday. Credit: Jim McIsaac

The mystery leading up to game time Wednesday night, in what could reasonably be called the Knicks most important game of the season, was whether Jalen Brunson could play. But it was an easy bet that Brunson would not miss it, taking the court with his sprained right hand protected by a brace.

But what the Knicks could not anticipate was that with Brunson back they would lose the player who has been an iron man for them this season — Julius Randle — to a sprained left ankle in the first half. So they were left to find a way to slog through what always seems like a street fight with the Miami Heat without Randle and with a limited Brunson.

The Knicks turned to a pieced-together second unit led by Immanuel Quickley, who had a game-high 24 points, and Quentin Grimes, who added 23, in the fourth quarter and ran away with the game down the stretch for a 101-92 win, reducing the magic number to one to secure a playoff berth.

“No Ju so we kind of had to figure something out,” RJ Barrett said. “Thank god it worked.”

While Knicks coach Tom Thibodeau has preached that every game is important, this game did have an added significance since the Knicks entered the night with a three-game lead on the Heat in the standings. With the win, the fifth-place Knicks not only upped the lead on Miami to four games, but gave them the tiebreaker in head-to-head meetings. The Nets remain in sixth place between the two, 2 1/2 games back of the Knicks.

The Knicks were without Randle and never went back to Brunson in the fourth quarter, riding the play of the second unit — Thibodeau not making a substitution in the entire period. Clinging to an 86-85 lead with 6:31 to play, the Knicks ran off eight straight points that started with Isaiah Hartenstein finding Josh Hart alone under the basket and Grimes hitting a pair of free throws. Then it was Hart taking the ball the length of the court for a dunk and finally Grimes taking an outlet from Hartenstein for a fast break dunk, prompting a Heat timeout — all in the span of 77 seconds. Brunson was at the scorer’s table to report in before the timeout, but Thibodeau called him back and rode the hot hand.

“They rolled away with the game,” Brunson said. “The way they were playing was incredible. They just found a way to keep fighting. Everything they were doing on both sides of the ball they were clicking so you’ve just got to go with that.”

“The most important thing is winning the game and that’s what I love about Jalen,” Thibodeau said. “So he was like, ‘I’m good.’ I said OK, hold on. He came back to the bench and he’s cheering his teammates on. That’s what you want. You’re asking all your players to sacrifice and put the team first. And that’s when we talk about leadership. It doesn’t get any better than that.”

Shortly before the Knicks took the court to face the Heat, with a chance to almost certainly eliminate any shot at the Heat catching them for the fifth spot in the Eastern Conference playoff race, the team announced that Brunson was available to play. But the most pressing question right now remains what the status is for Randle.

Randle has not missed a game this season, trailing only the Nets' Mikal Bridges in total minutes played. But he was done at 15 minutes on this night and the Knicks can only hope that he is ready by Friday in Cleveland.

“He’ll be evaluated tomorrow,” Thibodeau said. “It’s a sprain. So that’s about the extent of it, we’ll see where he is tomorrow. … It’s part of the game, injuries, you deal with it, and now just focus on the rehab, get back as soon as you can. We just went through it with Jalen. It’s the same thing, you don’t do it individually. You have to do it collectively. So we understand where we are and what we have to do. But we have more than enough on the bench. I thought our bench was terrific. So next, get in there, next man up, get it done. That’s the way we have to approach it.”

With the Garden feeling like a playoff game at the start the Knicks raced out to an 8-0 lead with a Mitchell Robinson dunk and a pair of three-point field goals by Grimes. But then things got, well, ugly. The Knicks went through a stretch in which they missed nine straight shots and turned the ball over four times as Miami ran off 14 consecutive points.

Randle and Barrett were a combined 0-for-8 from the field and scoreless in the first quarter and other than Grimes and Quickley no one seemed to be doing anything positive as the team was 0-for-6 from the free-throw line (the worst first quarter without a free throw since Atlanta did it on Feb. 23, 2009) and turned the ball over seven times.

But the Heat were similarly struggling and held a 23-19 lead after one quarter which was stretched to as many as 10 points in the second quarter. The Knicks managed to get on track and take a 48-46 lead into the intermission with Brunson delivering a buzzer-beating three-pointer.

The score was dimmed through by the reality that the Knicks saw Randle go down in pain. With 2:38 left in the half Randle came down on Bam Adebayo’s foot, turning his left ankle and he went to the floor. He tried to get up, but quickly realized he could not and was down for a long time before being helped to his feet.

He started toward the locker room, but remained in the game to shoot two free throws — which would have allowed him to return to the game. The Knicks quickly fouled and he went straight to the tunnel — appearing to collapse as he moved out of view. The Knicks announced that he was done for the night before the teams took the court for the second half.

Newsday LogoSUBSCRIBEUnlimited Digital AccessOnly 25¢for 5 months