ATLANTA — Josh Hart delivered his first playoff dud — at least scoring-wise — at the worst time.

For the opening two games, he was consistent for the Knicks. Entering the postseason, his 3-point shooting was something that could make the difference down the stretch — just like it did against the Celtics late in the regular season.

But with fellow starter Mikal Bridges benched and scoreless, Hart only managed two points during the Knicks’ gutting 109-108 loss to the Hawks in Game 3 on Thursday.

He finished 1-for-9 shooting at State Farm Arena and missed all four of his 3-pointers. Hart still produced nine rebounds, six assists and played strong defense on CJ McCollum after he was switched onto him in the second half, but when his scoring faltered, it left the Knicks too dependent on Jalen Brunson, Karl-Anthony Towns and OG Anunoby.

“I mean, yeah, they just didn’t go,” Hart said. “… I gotta make them.”

This has become a recurring issue for Hart throughout the first-round series, too. He entered Thursday with just one made 3-pointer, despite hitting a career-best 41.3 percent of his shots from beyond the arc during the regular season.

He had a bad turnover in transition late in the first quarter, as he dribbled the ball off his leg and out of bounds, and his only basket occurred with 7:35 remaining — when Towns fed him a pass and he deposited it through the net.

If there was a silver lining for Hart, and a glimmer of hope for the Knicks, too, Mike Brown switched him onto McCollum at the start of the second half, and Hart was effective in limiting the Hawks’ star — who erupted for 32 points in Game 1 and another 16 in the opening half Thursday — when matched up with him.

“I just tried to make it tough for him,” Hart said. “That was the biggest thing, just try to make it tough for him, force him into tough shots.”

But the ineffectiveness on offense will sting. And the 3-point shooting — and his specifically — has quickly become a Knicks problem.

“I feel like we had good shots,” Hart said. “We didn’t knock them down.”