Randazzo was hit directly in the mask by a 91-mph fastball from San Francisco's Johnny Cueto in the fifth inning but remained in the game until after the 13th inning Friday night. Second-base umpire Clint Fagan took his place.
Randazzo originally got hurt when Billy Hamilton squared to bunt Cueto's pitch but pulled the bat back at the last minute.
Catcher Buster Posey couldn't get his glove on it and the ball hit Randazzo and knocked him to the ground. Giants trainer Dave Groeschner rushed out to check on Randazzo.