A Manhattan chef suffered a broken jaw while walking in Philadelphia last week in what he believes could be a vicious example of a so-called "knockout" attack - but police aren't yet calling it that.

But police say they are investigating the assault on Diego Moya, 30, and hoping to locate surveillance video in hopes of finding suspects, said Officer Jillian Russell, a department spokeswoman.

According to police and Moya's own account to the New York Daily News, Moya had just finished eating pizza with some friends in Old City when he headed out toward the hostel he was staying at on the first block of S. Bank Street about 11 p.m. Tuesday. He had been in town visiting his parents for a pre-Thanksgiving visit.

While on Bank Street, Moya was attacked from behind. He told the New York Daily News he believes it was a group of males between the ages of 16 and 21.  Philadelphia police said Moya was not able to give a description of any attackers after they arrived about 11:30 p.m.

"He doesn't know who since he was hit from behind," Russell said.  She said that police were not calling it a knockout attack because details were so few. She said the assault did not appear, however, to be such an attack.

Regardless, Moya was knocked unconscious and woke up on a stoop, he said. He was taken to Pennsylvania Hospital.  He had to undergo a three-hour surgery that left his jaw wired shut, a devastating injury for a chef. It means he cannot work. The newspaper says that Moya's attackers also broke his nose in several place. He was left unconscious and bleeding on a stoop.

"I recall zero, was a few doors down from my hostel," Moya wrote in an email to the paper. "Woke up on a stoop with blood on my hand."

Moya said nothing was stolen, leaving him to conclude that the attack was a "game".

Several attacks in Philadelphia in recent weeks have been dubbed by some as part of the knockout game and Mayor Nutter has publicly warned teens not to engage in the game. Police have not confirmed there is such a trend, however, they did say that at least one incident in Fox Chase can be attributed to the game.

On his Facebook page, Moya says he works at Casa Mono in New York. He chronicled some of his stops in Philly on Facebook, including Reading Terminal and Eulogy Belgian Tavern.

He also wrote of his attack, from a hospital bed: "At Philadelphia hospital. Was attacked from behind. Broken jaw and orbital bone."

His father and sister have shared updates on his condition.

"Hi everybody, this is Diego's sister," said one update. "Diego's staying at my parents for now, not ready to see people yet, but he wants you to know he's ok, surgery went well, thanks everyone for all the love."