Belt, 26, is on the seven-day disabled list reserved for concussed players. He's eligible to be reinstated Sunday, but that's unlikely to happen at the current rate.
"It's hanging on a little more than we thought," Bochy said Wednesday of Belt's discomfort. "We have some concern there."
Chris Haft is a reporter for MLB.com. Read his blog, Haft-Baked Ideas, and follow him on Twitter at @sfgiantsbeat. This story was not subject to the approval of Major League Baseball or its clubs.