When the Knicks open the playoffs against Atlanta, they’ll be contending with one of the NBA’s hottest teams.

And Josh Hart may find himself guarding one of the league’s biggest breakout players.

While the Hawks enter this Eastern Conference first-round series seeded just sixth, they come into Saturday’s Game 1 at the Garden having won 19 of their past 24 down the stretch.

Atlanta’s Jalen Johnson averaged 22.5 points, 10.3 rebounds and 7.9 assists this season to earn his first All-Star nod.

While OG Anunoby is the Knicks’ wing stopper, the 6-foot-4 Hart shouldered most of the defensive burden on the much bigger Johnson in their last matchup, and helped the Knicks come away with an April 6 victory in Atlanta.

“Jalen is a really, really good player, a great player. And shoot, he’s won a lot of awards this year. He’s led the charge,” coach Mike Brown said. “Him and Nickeil [Alexander-Walker] have led the charge in their resurgence here at the end of season, so a lot of respect there. In our last game, Josh matched up with him a little bit more than OG. So it’s more a team thing than anything else.”

Hart smothered Johnson into just 2-for-7 shooting with three turnovers during the 8:16 he guarded the 6-foot-8 forward, with Johnson finishing the game 8-for-19 with five turnovers.

It’s unclear how much of that duty he’ll draw in Saturday’s Game 1.

What’s clear is he’s prioritized the dirty work on that end of the floor.

“The thing I’m most proud of myself on [this season] is I feel like I’m doing a better job of moving on to the next plays. If I’m not making shots, what else can I do to help this team be successful?” Hart said. “How can I bring energy? What kind of plays can I make to help guys get in position to be successful?

“I’m doing that and being able to turn the page on a bad play, bad quarter, bad half, a little better than I did before. So that’s been good. But the season, it was solid.”

But unfinished.

The Knicks regular season was good, but irrelevant.

Even team owner James Dolan set the bar as championship or bust, so the measuring starts now.

Hart admits as much.

“I had no expectations [coming in]. We made the playoffs, we had 50 wins, so that was good. You know, we know we’re going to be judged by what we do starting now,” Hart said. “So we didn’t really have expectations going into it. Just wanted to make sure we get to the playoffs.”

Now that the Knicks are here as the third seed in the East, Hart expects the Garden to provide an electric home-court advantage against the Hawks.

“Man, the energy is great in the regular season, but if you’re able to get to a playoff game, the energy is unreal,” Hart said. “They show up for us every single game. You have fans outside, [the] weather is good. So everyone’s outside wanting to have fun, wanting to see the Knicks play. So we need them, obviously now more than ever, and we want to show them love.”