RJ Barrett finally looked like his regular-season self Sunday, but it hardly made a difference on the final scoreboard.

Despite Barrett’s series-high 21 points, the Knicks fell to a 3-1 deficit in the best-of-seven series after Atlanta’s 113-96 Game 4 victory. He added six rebounds, four assists and two steals.

Barrett, who averaged 11.3 points in the first three games on a combined 13-for-38 shooting, was 8-for-15 from the field in Game 4.

“I just played harder. I didn’t really think about it,” Barrett said. “Coach [Tom Thibodeau] told me to be aggressive and be myself and that’s what I did.”

Ahead of Game 4, Thibodeau, discussing what it would take to get Barrett going, emphasized the importance of being aggressive.

“Do all the things you’ve done to get here. If you’re open, shoot and find a way to get easy buckets. … You get an easy bucket and now suddenly your energy changes and you get into rhythm,” Thibodeau said.

“I don’t want guys to overthink things. Just play freely, be aggressive, shoot your shot. If guarded, pass. Keep it simple.”

Though he missed his first three shots, Barrett got involved early with a four rebounds and four assists in the first quarter, and closed the quarter with a seven-point flurry in a two-minute stretch as the Knicks took an early lead.

The Knicks were still in the game at halftime, down 53-49, but the Hawks blitzed them in the third quarter.

“We can’t let them go on those runs,” Barrett said. “In the third, when they went on a run, we weren’t really able to stop it. We’ve got to be aggressive. We were aggressive in the first half and we got good results.”

Barrett scored 12 of his 21 points after halftime, but the Knicks never made a run after the Hawks’ 15-5 run to open the third.

Trae Young did most of the damage — finishing with 27 points and nine assists — but Barrett said it was a lot more than Young.

“They have a lot of guys, not just Trae,” Barrett said. “You’ve got to guard their whole team. We’ll figure it out, just go back and watch film. We’ll figure it out.”