SAN FRANCISCO -- The Giants called up Eli Whiteside from Triple-A Fresno before Sunday's game against the Braves, giving the club a third catcher behind Buster Posey and Hector Sanchez.

The Giants had sent down reliever Eric Hacker after Saturday's game and waited until Sunday to announce the corresponding move.

"We just wanted some coverage on the catching side if we get in a situation with Buster not being 100 percent," manager Bruce Bochy said. "We can run for him and still have another catcher."

Whiteside competed with Sanchez for the backup catcher roster spot in Spring Training and joined the club when Sanchez was on the disabled list for two weeks with a sprained knee last month.

Posey started at first base Sunday with Sanchez behind the plate for starter Tim Lincecum.

"Today, for example, [Posey]'s at first base, and if I want to take him out and put [Brandon] Belt out there for his defense, I'll still have another catcher," Bochy said.

Bochy said Posey is "real close" to being back to 100 percent from his tight right hamstring.

"He feels it running just a little bit," Bochy said. "He's taking it easy, but if we get in a situation where we need some speed out there, we don't want him to push it, and having another catcher will allow us to make that move."

Giants to be conservative with September callups

SAN FRANCISCO -- With rosters set to expand Saturday, Giants manager Bruce Bochy doesn't expect the Giants to add a considerable number of players to their roster, especially as they head into the last month of the race to the postseason.

"I'm not a fan of bringing up too many, to be honest," Bochy said. "I think it can get a bit crowded and it's hard to put them all in there. You bring up enough to give you enough coverage everywhere, the pitching side and the players side."

The roster limit will expand to 40 players, and the Giants are expected to use a combination of activating injured players such as Brad Penny and Aubrey Huff as well as calling up prospects to add enough depth for the last month of the season -- but not too much.

"That's a fine line," Bochy said. "It gets a little crowded with batting practice and in the clubhouse. I think you can overdo it sometimes to be honest, call up too much guys."