Fontenot started in place of Jeff Keppinger, who went 1-for-11 in the first three games of the series and has three hits in his past 22 at-bats.
Keppinger's bunt in the eighth inning Saturday night played a key role in the Giants' four-run rally that led to their 6-5 victory. The bunt occurred after Andres Torres led off the inning with a single. The Giants were trailing, 3-2, at the time.
Keppinger's bunt was too hard, but pitcher Huston Street threw wide of second base and into center field.
"We got a break on that, because it could have been a double play," manager Bruce Bochy said.
Keppinger was bunting on his own, Bochy said. Trailing by one run on the road, Bochy said he wasn't going to give the sign for a sacrifice, because Carlos Beltran, one of the Giants' better hitters, would then get intentionally walked.