He felt healthy enough to pinch-hit in the eighth inning. However, Belt admitted he was far from 100 percent.
"I felt like I was good enough to go out there and have an at-bat," said Belt, who struck out. "I don't think it was anywhere near what I'd like it to be."
Already without Hunter Pence (hamstring tightness) and Buster Posey (scheduled day off), the Giants were dealt another blow because of Belt's absence.
"You're going to miss those guys," said Giants manager Bruce Bochy. "Unfortunately it happens once in a while and it happened tonight."
Belt and Bochy do not believe this latest setback will be serious, though. Belt added he thinks he'll play in Sunday's series finale against the Braves, but isn't completely certain.
"I'll get here and we'll figure it out," Belt said Saturday. "I would say I have a good chance of playing tomorrow, but it's one of those things you just don't know.
"Getting to the time of the year where it doesn't take much for stuff to happen. You got to make sure you take care of yourself and hopefully everything goes well."
Justin Wise is a reporter for MLB.com based in the Bay Area. This story was not subject to the approval of Major League Baseball or its clubs.