The Giants recalled Sanmartin from Triple-A Sacramento on Thursday.
Sanmartin was just sent down Wednesday, but he'll return a day later to take the roster spot of the injured Keaton Winn (elbow). The left-handed Sanmartin has logged a 7.11 ERA, 2.05 WHIP and 6:2 K:BB over 6.1 innings during his time in San Francisco this season.