The Giants placed left-handed reliever Josh Osich on the 15-day disabled list with a forearm strain, the team announced Thursday afternoon.
The move is retroactive to July 24.
San Francisco selected Matt Reynolds from Triple-A Sacramento and added him to the 25-man roster.
Osich is 1-2 with a 4.25 ERA over 48 appearances this season.
He has inherited a National League-leading 40 runners and has allowed just two to score.
Reynolds signed a minor league deal with the Giants on June 24, after he was released by Arizona in late March.
He is yet to allow a run over over 10.1 innings with Double-A Richmond and Triple-A Sacramento combined.
He played for the Rockies from 2010 to 2012, and the Diamondbacks in 2013 and 2015.