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07/18/12 6:17 PM ET

Whiteside called up as Sanchez heads to DL

ATLANTA -- Hector Sanchez's sprained left knee forced him to the 15-day disabled list Wednesday, dashing the cautious optimism the Giants expressed one night earlier when the rookie catcher was injured.

San Francisco recalled catcher Eli Whiteside from Triple-A Fresno to replace Sanchez on the active roster.

Sanchez said after Tuesday's 9-0 victory over Atlanta that, at best, he might be sidelined for only a couple of days, a sentiment that manager Bruce Bochy echoed. But the MRI that Sanchez underwent Wednesday morning indicated that he could be sidelined for at least five to seven days, prompting the Giants to act.

"It's a tough call, because you don't know when Hector will be ready," Bochy said. "... Plus, you don't want this [injury] to linger all year."

Sanchez, who has established himself as a capable backup for Buster Posey, won't need surgery and believes that he'll physically be able to resume playing when he becomes eligible for activation on Aug. 2.

"I feel good because it's nothing bad," said Sanchez, who's batting .281 with two home runs and 24 RBIs in 39 games. Sanchez hurt himself as he returned to first base during Tuesday's fourth inning.

Whiteside has spent all or part of the previous three seasons with the Giants, hitting .233 in 187 games through that span. More importantly, he's familiar with the Giants' pitchers. He was batting .241 with one home run and 15 RBIs in 47 games for Fresno.

Giants mindful of Posey's workload

ATLANTA -- Manager Bruce Bochy will continue to consider factors such as fatigue and the Giants' need for offense in determining Buster Posey's playing time.

But Bochy knows he must pay closer attention to these elements while backup catcher Hector Sanchez is sidelined. Sanchez went on the 15-day disabled list Wednesday with a sprained left knee.

Posey has been completely idle for only nine of San Francisco's first 91 games, mainly because he has started 15 games at first base.

"This is more a case where we've been looking for production from first base," Bochy said. "Buster has been going over there to help out."

Having Posey at first base while the .281-hitting Sanchez caught bolstered the Giants' offense. But Sanchez's absence probably will limit Posey's appearances at first. Bochy also is aware that he must not tax the health of Posey, who's barely more than a year removed from sustaining extensive left leg injuries.

"At some point he's going to need a day off," Bochy said. For example, Eli Whiteside may catch Thursday afternoon's series finale here if Wednesday's game is a prolonged one.

The possibility of Posey's reduced time at first base sharpens the focus on Brandon Belt, who has struggled lately.

"I think it's fair to say that Brandon's a little off right now," Bochy said.

Belt, San Francisco's primary first baseman for most of the season, entered Wednesday hitting .163 (8-for-49) in his previous 18 games.

"I say this so many times: Young players are going to have their ups and downs," Bochy added. "They get better handling it. I know he's working hard in the cage, but at the same time you have to get production from everywhere, especially first base. Our hope is he'll get it going and contribute to this offense."

Chris Haft is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.