That’s a low blow!

Tempers boiled over Thursday in Philadelphia when troubled Mets great Lenny Dykstra met his future boxing opponent — woman-hating “Bagel Boss” guy Chris Morgan.

The pint-sized brawler from Long Island went to shake Dykstra’s hand — but got slapped in the face instead and winced in shame.

The retired MLB All-Star also pushed his 5-foot-tall future ring rival hard in the chest as the event’s host, AC Mike Lopez, announced the Atlantic City boxing bout’s date, Sept. 28.

The ragin’ bagel store customer had to be held back as he called Dykstra, 56, a “punk” and told him to “kiss my ass.”

“You’ve got a 1-inch d–k,” Dykstra yelled.

Morgan went viral last month following a meltdown at a Long Island Bagel Boss, which started when he thought one of the workers was “giggling” at him because of his diminutive stature.

“It’s about belittlement, what she was doing!” he yelled on video. “Giggling, all this crap! Being used by women, going on dates, they lie, say they like me and then use me for my money!”

Dykstra vowed to “f–king punish” Morgan for his viral tirade.

“You disrespect people, you disrespect women, you use the bagel shop’s name. Stand up!” he fumed.

The blowhards continued to trade verbal jabs, with Dykstra telling Morgan he was going to “humiliate you like a little b–ch.”

Morgan shot back: “I’ll just hand you a beer and let the shit to do the rest.”

“I am doing it because I know I can stand up to him,” Morgan said. “I am not doubting any of his abilities I’m just saying don’t underestimate me.”

Later, in an interview with The Post, Morgan said he was surprised by Dykstra’s behavior and suggested the ex-slugger was on the sauce.

“Had to be [drunk],” he said, as he munched on a Philly cheesesteak. “Did you see him talking? He’s a nut!”