The Giants optioned Sanmartin to Triple-A Sacramento on Wednesday.
Sanmartin will be squeezed off the 26-man active roster after the Giants needed to clear a spot for lefty Matt Wilkinson, who was called up from Triple-A to start Wednesday's game in Cleveland. After being summoned from Sacramento on Aug. 3, Sanmartin made eight relief appearances during his latest stint with the Giants, pitching to a 7.11 ERA, 2.05 WHIP and 6:2 K:BB over 6.1 innings.