RJ Barrett has thought about the play from time to time, particularly lately.

The Knicks were up three with under a minute left in the opening game of his playoff debut two years ago.

The Hawks’ Trae Young drove baseline and threw what looked to be an errant pass into the left corner.

Barrett got his hands on the ball, but slipped by the sideline.

Bogdan Bogdanovic picked the ball up and tied the score with a 3-pointer.

The Knicks lost by two, setting an ominous tone for the one-sided series they lost in five games.

“Just those little things,” Barrett recalled on Tuesday, “can change an entire series.”

Maybe the series would have gone differently had the Knicks won the first game.

Going to Atlanta up 2-0 (the Knicks won Game 2) is a lot different than being tied at one game apiece. Instead, the Knicks never really recovered after being unable to close out the opener.

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“That’s something I always remember,” Barrett said, referring specifically to the play in question.

The Knicks feel like a whole different team this season in their return to the playoffs. Most notably, they have more experience — led by point guard Jalen Brunson and his 28 career playoff games, 19 of them last spring for the Mavericks.

Two years ago, Julius Randle, Obi Toppin, Immanuel Quickley and Barrett were all going through it for the first time. They are older, wiser and better equipped for the postseason now, the Knicks believe.

“We’re a lot better than we were. The guys that are on that team that were in that playoff run, we’ve all grown and we’ve all gotten better, so that helps,” Barrett said, as the Knicks prepared for the opening-round, best-of-seven playoff series, which will start Saturday in Cleveland. “Experience helps. Guys that we have now, in addition, have been working well and we’ve just become better as a team.”

Brunson enjoyed a lot of postseason success last year, helping the Mavericks reach the Western Conference finals as the fourth seed.

In the opening round, he averaged 27.8 points across six games, making up for the loss of Dallas star Luka Doncic for the first three games of the series due to a strained left calf.

Given an opportunity, Brunson took advantage of it.

Other Knicks, who have yet to have their playoff moments, will be given a similar chance in this series.

“You can say whatever you’ve got to say to them, but in order to gain experience you need to get experience,” Brunson said. “All we’ve kind of said is, ‘Hey, it’s a different level. We’ve got to turn it up. Be yourself, do what you do best, but you’ve just got to turn it up.’ That’s just how it is.”

The Knicks, who finished the regular season 47-35, weren’t expected to be here.

Their preseason Over/Under number for victories was 39.5. Just reaching the play-in tournament would’ve been deemed a success.

Even after finishing fifth in the Eastern Conference, they aren’t being given much of a chance to advance.

They are a major underdog. Randle’s sprained left ankle, which has cast doubt on his availability and effectiveness for the series, has something to do with that.

The 51-win Cavaliers were four full games better across 82 regular season games and have home-court advantage.

But the Knicks are certain they are better prepared for the playoffs than they were two years ago.

The odds heavily favoring Cleveland won’t faze them.

“We’ve believed in ourselves since Day 1, and we’re going to continue to believe in ourselves,” Barrett said. “At the end of the day, you’ve got to go on the court and show it and prove it, so that’s what we’re going to try to do.”