The Knicks’ usually dependable defensive principles betrayed them for much of the game Monday night against an undermanned opponent.

It didn’t even matter in the end that Julius Randle absolutely could not be stopped at the other end.

The All-Star forward poured in a career-high 57 points, but the Knicks allowed 79 in the first half and ultimately fell short, as their three-game winning streak ended with a 140-134 loss to the Timberwolves at the Garden.

“Not very good. [We gave up] 42 points in the first quarter. They got going — good offensive team. It’s hard to shut them off once they get going like that,” Tom Thibodeau said. “They got everything they wanted. They had their way.

“We got in a big hole, fought to get out of it. And then came up short in the end. But we were playing with fire the whole game. … It’s hard to win like that.”

They lost despite Randle becoming the first Knicks player to score 50 since Carmelo Anthony pumped in a franchise-record and MSG-best 62 points in January 2014. That also was the most recent time a Knicks player had scored at least 50 in a game. Randle had equaled his previous career-best scoring output with 46 points against the Wizards in February.

“I’m such a results-driven person, I try to focus on process a little bit more, and are we taking the necessary steps to get better and build as a team?” Randle said when asked if he was able to take the positives out of his big offensive night. “Hopefully I will be able to, but tonight probably not. I’m a little bit upset about the loss.”

Jalen Brunson scored 23 points in his second appearance since returning to the lineup Saturday after missing 5 ½ of the previous six games with a bruised left foot.

Immanuel Quickley added 19 points and RJ Barrett had 13, but Thibodeau’s team fell to 12-4 since Josh Hart (10 points) joined the lineup in a trade-deadline deal with Portland.

Taurean Prince scored 35 points and Mike Conley added 24 for the banged-up T’Wolves, who were without their best two players — Karl-Anthony Towns (calf) and Anthony Edwards (ankle) — due to injuries.

The fifth-place Knicks (42-31) are now three games behind the No. 4 Cavaliers and two ahead of the No. 6 Nets entering a two-game Florida swing that opens Wednesday in Miami.

The undermanned Timberwolves incredibly made their first 10 shots from the floor and their first five attempts from 3-point distance to grab a 28-21 lead just past the midway point of the opening quarter. The Knicks cut their deficit to 42-32 entering the second, but the T-Wolves finished the period at nearly 73 percent from the floor, hitting 16 of 22 shots.

The Knicks drew as close as eight in the second quarter, with Randle finishing the half with 26 points on 8-for-14 shooting and 7 of 8 from the free-throw stripe. But Prince netted 20 and Conley added 13 for a 79-70 Minnesota lead at intermission.

Randle positively took over the game with 26 points in the third, however, reaching 40 on two more free throws with 6:58 to go. He got to 48 to exceed his previous career-best and then surpassed 50 for the first time with consecutive long-range buckets for a 101-101 game with three minutes remaining.

With Randle sitting to open the fourth, a driving layup by Hart and a swished trey by Barrett provided the Knicks with a 115-111 advantage.

Brunson and Randle returned with 7:29 remaining, but Jaden McDaniels tied it from beyond the arc with three minutes left. Conley’s three free throws put Minnesota up by one less than a minute later and Prince knocked down a left-side triple to contribute to a 137-131 game with 1:27 left.

Randle’s converted three-point play got the Knicks back within one possession again, but he was whistled for a technical foul after failing to secure a defensive rebound before Conley sealed it at the stripe.

“It’s a shame to waste a performance like that. You couldn’t ask for anything more,” Thibodeau said of Randle. “But we were careless with the ball, turned the ball over. … All we had to do is keep making a simple play. We gotta make better decisions.”