Pistons defensive stalwart Isaiah Stewart won’t play Monday night in Game 2 against the Knicks because of right knee inflammation.

Stewart was listed as questionable with right knee inflammation ahead of Game 2 before being reported as “out” less than three hours before the game.

It’s a major loss for the Pistons, who rely on Stewart to be their air traffic controller on defense.

His status for the remainder of the first-round series remained unclear as of Monday.

Pistons coach J.B. Bickerstaff said Stewart’s availability will be determined on a “day-by-day” basis.

Stewart had limped into the playoffs as the same right knee issue sidelined him for the Pistons’ final two regular-season games.

Stewart, a product of Rochester, N.Y., labored through most of his 19 minutes of action in the Knicks’ 123-112 win Saturday.

He was seen wincing after an alley-oop dunk in the first quarter.

He appeared to be dealing with discomfort in his right leg before he checked out for the final time at the 9:06 mark of the fourth quarter.

SNY reported that Stewart underwent imagining on his right leg Saturday night.

Stewart’s availability moving forward will have major implications on this first-round series for the Pistons.

He has been the best rim protector in basketball since Spurs star Victor Wembanyama went down with an injury mid-February.

Stewart is the Pistons defensive anchor.

Not only does he patrol the paint, but his versatility and size allow him to move in space and guard the perimeter as well.

Whenever Stewart is off the floor, his absence is felt.

Take the fourth quarter of Saturday’s game as a prime example.

Stewart headed to the locker room at the start of the Knicks comeback.

When he left the game, the Pistons were up by six.

Over the final 9:06, the Knicks outscored Detroit 31-14 to take a 1-0 lead in the best-of-seven series.

Stewart finished Saturday with five rebounds and two blocked shots in his playoff debut.

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He was also a team-best plus-eight.

Even with Stewart sidelined, Knicks coach Tom Thibodeau believes the Pistons can present a tough defensive challenge for his team.

“They have versatility,” Thibodeau said pregame. “They have other guys that can step in and play that position… That’s sort of the nature of our league — the next guy gets in there and I always say you can’t be here without being a great player and that’s one through 15.”

Expect Jalen Duren and Paul Reed to be among those who will try to fill the void left with Stewart’s absence.

Duren — who made his playoff debut Saturday, recording seven points, six rebounds, three assists and three blocked shots — has consistently shown growth as a defender throughout this season.

The third-year center is averaging 10.3 rebounds and a career-high 1.1 blocks per game.

“JD has to step up for us and absorb a lot of those minutes, which he’s proven to be capable of,” Bickerstaff said. “He’s done it for us all season long, so I think it starts there with him.”

Meanwhile, Reed, the team’s No. 3 center, didn’t appear in Saturday’s game, but likely will make his 2025 playoff debut Monday.

In 45 games this season, he averaged 4.1 points and 2.7 rebounds.