Four teams went after Knicks center Mitchell Robinson at Thursday’s trade deadline, including the Bulls and Pistons, according to an NBA source.

Ultimately the Knicks pulled back, didn’t make any trades and now risk losing their longest-tenured player as an unrestricted free agent this July.

According to the source, two of the teams who had contacted the Knicks about Robinson got the impression they will lose him if he becomes an unrestricted free agent this summer.

The source said the relationship between Robinson and the Knicks currently isn’t on firm ground.

The Bulls were intrigued by Robinson, according to the source, because they were looking for another defensive center to go along with Nikola Vucevic as they eye a long playoff push.

The Knicks’ decision to not trade Robinson for assets shows they at least feel Robinson would accept a contract extension if one is offered. They can offer him a extension of five years, $55 million.

Robinson is injury-prone, hasn’t been paid as a starter after signing a four-year, $5.8 million deal as a 2018 second-round pick.

If the Knicks lose Robinson to free agency with no compensation, Knicks president Leon Rose will regret not pulling the trigger, especially if this season results in a lottery berth.

Rose didn’t talk to the media after the trade deadline — leaving his length of silence at nearly five months.

Another NBA executive says Knicks strategist Brock Aller was in favor of trading Robinson as he’s in charge of assets management. Knicks coach Tom Thibodeau, meanwhile, is believed to be a big fan of Robinson and perhaps he won out.

Aller actually called the Pistons and offered a complex package. The Knicks were interested in draft picks and also asked about rookie center Isaiah Stewart of Rochester. The Pistons weren’t willing to deal Stewart.

In Portland on Saturday, Robinson had one of his strangest games. He picked up three fouls early and wound up not logging a rebound. He scored two points in 14 minutes before leaving with an ankle sprain in the third quarter.

Robinson tweeted after the heartbreaking loss when the Knicks blew a 23-point lead: “Can’t speak for everyone but I gotta hold myself accountable to play at a high level every night. Tonight I was too relaxed and had no urgency. I sold.”

At a morning shootaround in Utah last Monday, Robinson was given several opportunities to say he wanted to remain a Knick long term. Instead, the 7-footer said it’s all in his agent’s hands. Thad Foucher of the Wasserman Group is repping Robinson now — his fifth agent.

The Pistons, Bulls, Mavs and his hometown Pelicans should each have interest this summer. One person close to Robinson said the Louisiana native would be interested in the returning to the Bayou State.