ATLANTA — It was reminiscent of those games in a driveway when an older brother bullied his younger brother, when he’d let him dribble around a bit before swatting his shot or stealing the ball away effortlessly.

That’s what the Knicks defense looked like against the Hawks as they bludgeoned them 140-89 in Game 6 on Thursday night to advance to the Eastern Conference semifinals.

They suffocated the Hawks from the opening tip, recording seven steals and three blocks — and forcing eight turnovers — in the first quarter.

They held the Hawks to just 6-for-16 shooting from the field and 1-for-6 shooting from 3-point range in that first quarter. And by the end of it, they led by 25 — which quickly doubled in the second quarter.

For the game, the Knicks held the Hawks to 37.8 percent shooting from the field and 25.7 percent shooting from 3-point range. They recorded an absurd 16 steals along with six blocks.

“We were able to get stops, run in transition, get layups,” Jalen Brunson said. “It really came down to our defense. It allowed us to play fast. Allowed us to play in transition. And we made shots.

“Most importantly, it shows us what we’re capable of defensively. I think that’s really important.”

Josh Hart, who was questionable for the game with a back injury, once again guarded CJ McCollum and completely neutralized him. McCollum was just 1-for-5 from the field when Hart guarded him, per the league’s official tracking stats. In total, McCollum finished with just 11 points on 4-for-13 shooting from the field.

The Knicks’ ability to stop McCollum in the final three games was central to completely changing the course of the series.

“I think I had good physicality,” Hart said. “I was able to force him into some tough shots. I was just trying to make life hard for him. Obviously, that’s a guy that’s got a lot of buckets in this league. That was something I thought, after Game 1 and Game 2 he kind of went off and kind of took over the game, that’s the matchup that I wanted going into Game 3 and after. I’ve had some conversations with the coaches about not taking me off him and those kinds of things.”

In truth, their defense as a whole helped them respond to a 2-1 series deficit with three straight routs. Across those last three games, the Knicks held the Hawks to just 102-for-248 (41 percent) shooting from the field and forced them into 47 turnovers.

Even during the first three games of the series, the Knicks never really let Jalen Johnson or Nickeil Alexander-Walker get going. It was McCollum who was hurting them.

Once they figured that out, this matchup turned into a mismatch.