DETROIT — James Dolan declared Monday the Knicks must “absolutely” reach the NBA Finals.

Then his team absolutely stunk.

On the same day Dolan set the bar higher than any previous finish under his ownership, the Knicks were blasted by the Eastern Conference leaders, destroyed 121-90 by the Pistons, prompting a postgame discussion among players, according to Jalen Brunson.

“If we want to be the team we say we want to be, then we’ve got to be better,” Brunson said. “Simple as that.”

Monday night’s embarrassment was a collaborative effort. But two prominent starters, in particular, pulled disappearing acts.

Karl-Anthony Towns and OG Anunoby combined for just 11 points on 2-for-7 shooting, with neither particularly aggressive nor engaged.

In fact, Towns, who scored six points, played just 22 minutes and it wasn’t because of foul trouble. It continued a downward trend in the roller-coaster season for Towns, whose production compared to last season has fallen off.

“We’ve got to get to the drawing board,” Towns said. “We’ve got to figure it out. Offensively, defensively, we’ve got to figure it out. It just hasn’t been good basketball from us recently.”

All the Knicks were outplayed by Pistons star Cade Cunningham, who finished with 29 points and 13 assists in 29 minutes. Cunningham sent the Knicks (23-13) to their season-worst fourth straight defeat, a stretch that’s been defined by Swiss cheese defense.

Their porousness continued at Little Caesars Arena, but issues abounded on both sides of the ball.

Through three quarters — and with the Knicks trailing by 20 heading into the final period — Jalen Brunson was the only Knick with more than 10 points. They were stagnant, slow and overwhelmed by Detroit’s physicality and athleticism while totaling a paltry 15 assists with 20 turnovers. The Pistons lead ballooned to 33 points in the fourth quarter, just a couple of hours after Dolan told WFAN that the Knicks “should win the Finals” and “getting to the Finals, we absolutely got to do.”

The owner also said he doesn’t anticipate a big move before the trade deadline next month, whether for Giannis Antetokounmpo or somebody else.

A few more performances like Monday should change minds.

“It’s pretty simple. They just physically kicked our ass,” Knicks coach Mike Brown said. “There’s no ifs, ands or buts about it.”

It was the first matchup for the Knicks this season against the upstart Pistons (27-9), who have risen early to the top of the East behind an MVP-like start from Cunningham.

The Knicks fell from second to third and are four games behind the Pistons. It felt like a litmus test except there were a few disclaimers: the Pistons were short-handed without two injured starters (Jalen Duren and Tobias Harris) and were also playing on the second game of a back-to-back, having flown from Cleveland following a Sunday afternoon contest at Rocket Arena. The Knicks, meanwhile, are in a slump and clearly missing the presence of Josh Hart, who sat his sixth straight game.

“Man, did we play defense tonight?” Miles McBride asked, rhetorically. “S–t. I mean, we just got to come together, figure out a way to get stops.”

All things considered, the Knicks are clearly behind the Pistons. They’re losing in the standings, they’re losing in head-to-head matchups, they’re losing on defense and they didn’t look Monday like they could live up to the owner’s expectations.

“[The Pistons] were ready to go tonight. They wanted to play,” said Brunson (25 points, no assists), who made some shots Monday but was a big part of the scarce ball movement. “They truly wanted to win and we didn’t.”

And the Knicks certainly didn’t look like they could live up to Dolan’s expectations.