Lenny Dykstra dealt a low blow Monday by backing out of the brawl against the “Bagel Boss Guy” Chris Morgan days ahead of the showdown — and now organizers of the match are threatening legal action.

The 56-year-old retired slugger was on Howard Stern’s “Howard 101” show Monday morning saying the fight is called off to focus on a legal malpractice suit he filed.

“Unfortunately, the fight with the bagel-whatever-he-is will not be happening because I have a trial that’s going on and my attorneys have informed me I have a duty and an obligation to prepare for that trial,” Dykstra said.

About 90 minutes later, his lawyer confirmed the match — scheduled for Saturday in Atlantic City — was nixed in a press release.

“Mr. Dykstra is withdrawing from his celebrity boxing match with Chris Morgan, the ‘Bagel Boss Guy,’ so that he can focus properly on preparing for his upcoming trial,” his attorney, John Pierce, said in a press release. “The fight will not be rescheduled.”

The troubled former Met is suing Boucher Law Firm related to a previous suit he’d filed alleging he was beaten by sheriff’s deputies while incarcerated at the Men’s Central Jail in Los Angeles.

Dykstra, who lives in New Jersey, sued his former lawyers claiming they messed up his chances of suing Los Angeles County. The case is set to begin jury selection Oct. 21.

But now the baseball legend may soon find himself in even more legal trouble — with boxing organizers who say he’s already collected a $15,000 paycheck for the fight.

Celebrity Boxing promoter Damon Feldman claimed Dykstra has also spent the last two weeks in a hotel on organizers’ dime.

“It’s like he robbed us. He’s a bum,” Feldman told The Post, saying he wants to sue to get the money back. “This is an absolute disgrace. It’s a black eye in the face of celebrity boxing.”

Dykstra allegedly backtracked when a blindsided Feldman confronted him Monday morning on the phone after his announcement.

“I got him on the phone. He told me he’s fighting,” Feldman said.

But by early Monday afternoon, organizers said the fight was officially off.

Celebrity Boxing is now looking to replace Dykstra with “The Partridge Family’s” Danny Bonaduce or Chad Johnson from the “Bachelor.”

Reps for Dykstra didn’t immediately respond to a request for comment. Morgan also couldn’t be immediately reached.