Pence, a two-time MLB champion with the Giants, was struck by a pitch from the Chicago Cubs' Corey Black during Spring Training on Thursday.
The Giants went on to win the pre-season game 8-6, but paid the heavy price with Pence to be unavailable until late April.
The ballclub confirmed Pence will be sidelined for 6-8 weeks.
"It didn't look good," Giants manager Bruce Bochy said.
"You hate to see it but these things do happen. Guys work so hard to get ready."
Pence is a big part of the Giants' roster, playing in all 162 games last season to help the team win the World Series.
The Giants open their season against the Colorado Rockies on April 13.