CLEVELAND — The Knicks, due to injuries, didn’t play many games at full strength over the final month of the regular season, but their returning top players fronted them to an all-important victory in their playoff opener on Saturday.

Julius Randle scored 16 of his 19 points in the first half and grabbed 10 rebounds in his first appearance in more than two weeks, and Jalen Brunson bounced back from early foul trouble to net 21 of his 27 points after halftime for a taut 101-97 victory over the Cavaliers in Game 1 of the Knicks’ first-round playoff series at Rocket Mortgage FieldHouse.

“Obviously those are our guys, and we rely on them heavily on both sides of the ball,” midseason acquisition Josh Hart said after the game. “For [Randle], his first game back, I’m not sure what he did on the offensive side, but he was rebounding the ball, contesting shots.

“Him and obviously [Brunson] just controlling the tempo, getting us into our sets, doing those kinds of things that sometimes don’t show up in the box score. Having them both back, and us being at full strength, it feels good.”

Hart also had his typically dynamic all-around game off the bench, with 17 points and 10 rebounds (five offensive) in his postseason debut. And Obi Toppin scored all nine of his points in a pivotal third quarter run for the Knicks, who will look to grab a 2-0 series lead in Game 2 on Tuesday in Cleveland.

“Tonight obviously didn’t go the way we wanted to, but we’ll be ready for Game 2,” All-Star guard Donovan Mitchell said.

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Mitchell, a Westchester County product, scored a game-high 38 points on 14-for-30 shooting, with Darius Garland adding 17 for the fourth-seeded Cavaliers.

Randle took pregame warm-ups and was reinserted into the lineup after he missed the final five games of the regular season with a sprained left ankle suffered March 29 against the Heat.

The Knicks’ lone All-Star buried his initial 3-point attempt and followed that with a driving bucket as the Knicks jumped out to a 9-2 lead. But the Cavaliers netted the next nine points, and Brunson sat down after picking up his second foul just 4:02 into the game.

“There’s no time to dwell on that, I was just trying to keep everything positive,” Brunson said. “I knew my time would eventually come around.”

Randle normally plays the entire first quarter, but coach Tom Thibodeau altered his usual rotation pattern and subbed out his leading scorer just 40 seconds later, replacing him with Toppin.

“We talked about it before the game. If Julius needed to come out, come out. Get a breather and get back in,” Thibodeau said.

Randle was fouled by Jarrett Allen after grabbing an offensive board in the second quarter, then was bumped by Mitchell as he walked away. He then raised both arms in the air and appeared to egg on the booing crowd with his hands.

Mitchell finished the half with 18 points — two more than Randle — but the Knicks led 50-45 at intermission despite missing 13 of 16 from long distance.

After Randle was pulled again early in the third, Toppin raced ahead of the field for a one-handed dunk to regain the lead for the Knicks with his first points of the game. Toppin totaled nine points during a 22-11 surge for the Knicks, and Brunson managed 12 points in the quarter without committing another foul as the Knicks carried a 78-70 lead into the final period.

Mitchell and Brunson — who had missed 10 of the final 14 games with foot and hand ailments — exchanged long-range makes to keep it an eight-point game midway through the fourth.

Another Mitchell trey cut the Knicks’ lead to 92-87 with 3:48 to go, and consecutive layups by Mitchell and Cedi Osman off turnovers by RJ Barrett and Brunson trimmed the lead to one.

Allen’s tip-in then gave Cleveland its first lead since the opening quarter, 93-92 with 2:12 left. But with 1:49 left, Hart buried a straightaway 3-pointer as the shot clock expired to put the Knicks back up, 95-93.

Brunson knocked down two big shots in the final two minutes, Randle snared a key offensive rebound and Quentin Grimes sank two free throws with 4.1 seconds left to seal it.

“To be able to depend on each other is so important,” Thibodeau said. “We need everyone, so everyone has to be willing to sacrifice and put everything they have into it and just find a way to win.”