The Kern County coroner says 35-year-old Jose Luis Ochoa was declared dead at a hospital about two hours after he suffered the injury in neighboring Tulare County on Jan. 30.
An autopsy concluded Ochoa died of an accidental "sharp force injury" to his right calf.
Sheriff's spokesman Ray Pruitt says it's unclear if a delay in seeking medical attention contributed to Ochoa's death. Tulare officials are investigating, and no arrests were made at the cockfight.
Cockfighting is a sport, illegal in the United States, in which specially bred roosters are put into a ring and encouraged to fight until one is incapacitated or killed.