CLEVELAND — It was peak Tom Thibodeau, already looking ahead to the next game after a massive victory.

As pleased as the Knicks’ coach may have been after a thrilling Game 1 win over the Cavaliers in this best-of-seven, opening-round series, he wasn’t ready for his team to take a bow.

“We know we’re gonna have to play a lot better than we did [Saturday night],” Thibodeau said after the Knicks’ first road playoff win since 2013.

Despite holding the Cavaliers to 97 points and limiting them to 43.4 percent shooting from the field, Thibodeau didn’t love his team’s defense. They didn’t have an answer for Donovan Mitchell, who went off for 38 points and eight assists.

“We obviously have to do a lot better. And he’s a tough cover,” Thibodeau said. “Take a look at the film. See how we can improve. We know we’re going to have to be tougher, play better.”

Cleveland only shot 10-for-31 from 3-point range, and its two big men, Evan Mobley and Jarrett Allen, were a combined 5-for-19 from the field.

Three of the Knicks’ top perimeter players, RJ Barrett, Quentin Grimes and Immanuel Quickley, struggled on the offensive end in the opener, shooting a combined 3-for-21 from the field. Grimes, though, was a key factor on the defensive end and sank the clinching free throws with 4.1 seconds remaining. Barrett missed 10 of his 12 shots, but did have six assists and four steals. Quickley was plus-eight in 24 minutes.

“Doing everything, that’s how you win games,” Barrett said. “Hustle, and it’s really a team effort.”

The series-opening victory was similar to the Knicks’ crushing Game 1 loss to the Hawks two years ago. They led for most of the second half of that game, too. But Barrett couldn’t come up with a key loose ball in the final minute that led to a Bogdan Bogdanovich game-tying 3-pointer in a two-point loss. This time, Julius Randle did come up with a 50/50 ball in the final seconds, and the Knicks prevailed.

“Funny how things turn, right?” Randle said. “We were in the exact same position two years ago. So it’s funny how things turn. That experience was important for us. It brought us to this point here. Great first game for us.”