Belt, 30, went down in Wednesday's loss to the Seattle Mariners. He was 1-for-3 in the game before being replaced.
In his eighth MLB season, Belt came into Thursday hitting .278/.372/.470 with 14 home runs and 43 RBI. He's been a solid cog in a Giants lineup that has manufactured runs despite not having a ton of power.
Over the last four seasons, Belt has dealt with intermittent injuries. He played in a career-high 156 games in 2016 but dealt with injuries in the three years otherwise. He was limited to 61 games in 2014 by a combination of ailments, missed 25 games in 2015 and sat out 58 times in 2017.
Buster Posey and Pablo Sandoval will likely see additional time at first base if Belt is out for an extended period. Posey occasionally plays first base on days when he needs a rest from catching.