Puerto Rico's Kermit Cintron kept his International Boxing Federation welterweight crown on Friday by stopping US fighter Jesse Feliciano in the 10th round but broke his right hand in doing so.
Cintron said he broke his hand on the first punch he landed at the start of the fight but did not show any signs of pain until moments after a flurry that prompted referee Jon Schorle to halt the fight 1:53 into the 10th round.
"The first right hands I threw in the first round, that's when I hurt it," Cintron said. "I heard the crack. The very first right hand I threw I hurt it."
The injury could delay a planned Cintron showdown with unbeaten US fighter Paul Williams on Feb. 2.
Cintron improved to 29-1 with his 27th early stoppage in a successful second defense of his title. Feliciano fell to 15-6 with three drawn.
"Jesse Feliciano fought a hell of a fight. He fought well and I didn't," Cintron said. "I was trying to fight him inside. I didn't fight a good fight. Now I have to just go back to the drawing board and go from there."
Unbeaten rival champions Floyd Mayweather and Miguel Cotto remain the star fighters in the division. Mayweather faces England's unbeaten Ricky Hatton next week while Cotto could face the winner.
Cintron dominated early with powerful rights but Feliciano went toe-to-toe with the champion in the fifth round.
After the ninth round, Feliciano followed Cintron back to his corner and taunted him, vowing to stay with him to the finish. When Cintron came out of his corner, he made sure the end was quick.