SAN ANTONIO - Welterweight contender Oscar Diaz had surgery for bleeding on the brain after collapsing between rounds of a nationally televised bout in his hometown.

Oscar Diaz, left, takes a punch from Delvin Rodriguez during their USBA welterweight title fight at Municipal Auditorium in San Antonio, Texas Wednesday July 16, 2008. Diaz spent the night in surgery after collapsing between rounds of the nationally televised bout in his hometown. (AP Photo, San Antonio Express-News, Tom Reel)

The 25-year-old fighter was taking a beating from Delvin Rodriguez on Wednesday night at San Antonio's Municipal Auditorium when he collapsed on his stool before the 11th round.

Ron Katz of Star Boxing, which promoted the fight, told The Associated Press that Diaz was heavily sedated following surgery.

"My understanding is they had to remove on the left side a part of his cranium to get the swelling down," said Katz, citing information he said came from promoter Donna Brooks. Katz said Brooks was at University Hospital with Diaz.

Katz said Diaz was not in a medically induced coma, which he considered a good sign.

"It's touch-and-go, very critical," Katz said. "But the doctor, from what I've gathered from Donna, was optimistic."

Katz said injuries like Diaz's are usually career-ending. He came into the fight for the USBA welterweight championship with a 26-2 record and 12 knockouts.

"What one hopes for is that he pulls through," Katz said, calling Diaz a "strong kid."

Katz, who was at the fight, said Diaz had been taking heavy blows before he collapsed, but that "he was in there pitching."

There was no indication anything was wrong, Katz said, until Diaz stood up to begin the 11th round. Then he put his hands to his head and "yelped" before collapsing.

Referees immediately stopped the fight, declaring Rodriguez the winner by technical knockout, and doctors jumped into the ring to attend to Diaz. He was placed him on a stretcher and taken to University Hospital.

"EMS reacted so quickly and got him to the trauma center so fast that that really gave him a fighting chance," Katz said.

Hospital spokeswoman Leni Kirkman said she had no new information Thursday morning. She did not immediately return a phone call later in the day.