The Giants recalled Warren from Triple-A Sacramento on Friday.
The move corresponds with Kyle Harrison being placed on the 15-day injured list due to left shoulder inflammation. Warren made his lone major-league appearance Aug. 28 against the Brewers, during which he pitched two scoreless innings while allowing one walk and one hit. Across 23 outings in Triple-A this season, Warren has a 4.91 ERA and 1.27 WHIP across 22 innings. Warren will be available out of the Giants' bullpen for Friday's game against the Padres, per Andrew Baggarly of The Athletic.