MILWAUKEE — As the Knicks transitioned to their high-scoring style with an offensive backcourt, the onus fell on Arjay Barrett to pick up the slack on the perimeter defense.

That showed up in a variety of ways, but none more so than the distance Barrett covered on the court.

“Oh, I’m running,” he said.

Heading into Friday’s game against the Bucks, Barrett was seventh in the NBA in yards per game at 2.76. He was also fifth in passing yards on defense — the only Knick in the top 20 — indicating he’s destined to be the opposition’s biggest threat on the perimeter.

Much of this is due to necessity. The Knicks’ backcourt of Jalen Brunson and Evan Fournier is undersized defensively, so Barrett — who is physically strong but not the fastest — becomes the best option to guard the likes of Ja Morant and Gordon Hayward. Quentin Grimes’ foot injury, which has kept him out of action this season, has compounded the problem because he is Tom Thibodeau’s best alternative to protect the perimeter.

That kind of physicality certainly could have undermined Barrett’s output, which has fallen to low and ineffective levels in the first four games. Barrett pondered the excuse, but ultimately disagreed.

“I don’t know. I feel like I guarded people last year and it ended up being pretty good,” said Barrett, who entered Friday’s game shooting just 37 percent overall and 14 percent from beyond the arc. “I could definitely play better in attack and I feel like my rhythm is coming back after not playing for a while.”

Thibodeau scoffed at the idea of ​​Barrett taking on more responsibility on defense compared to previous seasons.

“No. It’s ridiculous,” Thibodeau said.

As Barrett pointed out, it had been moving like this for a while. He’s never topped 2.76 miles per game, but the No. 3 overall pick in 2019 has been the Knicks’ leading rusher in all three seasons.

He was also an ineffective scorer in the NBA, shooting less than 42% for his career.

“I like being a player where even if I’m not having my best night offensively, I can still be out there on the floor making a difference,” he said.

Arguably the Knicks’ best wing defender who played alongside Barrett — Reggie Bullock — left before last season with the Mavericks as a free agent, and Grimes can’t replace him in his absence.

It wouldn’t be surprising if Barrett was guarding Donovan Mitchell in Sunday’s game against the Cavaliers, which would be intriguing because of the summer trade talks.

Barrett, who the Knicks traded to the Utah Jazz for Mitchell, isn’t promoting the sideshow.

“What difference does it make? I’m here. He’s there,” Barrett said.

Also, he had a lot of defensive responsibilities in Milwaukee and had a chance to rediscover himself.

“It will fall. She’s going to fall,” Barrett said. “Especially the last game [Wednesday’s overtime victory over the Hornets] felt great, everything felt great, especially that last shot – the last one I missed in overtime. I thought it was definitely good.

“So it’s going to happen, it’s going to fall.”