By Mark Vester

Undefeated welterweight contender Omar Chavez (21-0, 15KOs), son of the legendary Julio Cesar Chavez Jr., tore his right bicep in sparring on Thursday. After visiting a doctor, he was told to rest for at least a week. As a result he withdrew from his upcoming fight on May 1 in Culiacan, Mexico. His fight was going to be the headliner on that night's edition of the Fox Sports televised "Top Rank Live" series.

The new main event will feature super flyweight Tomas Rojas (32-11, 22 KOs), returning from a December KO loss to Vic Darchinyan, to face Jean Piero Perez (14-3-1, 10 KOs).

"I felt a sharp pain in my bicep after throwing a strong cross while I was sparring. I could not continue boxing and I went to Dr. David Cuen, who found the tear and told me that I needed to rest for a week," Chavez said to The Record.

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