The Giants optioned Koss to Triple-A Sacramento on Friday.
The move opens up a roster spot for Daniel Susac (elbow), who was reinstated from the 10-day injured list Friday. Despite making the Giants' Opening Day roster, Koss has appeared in just 10 games and has gone 1-for-14 with one run scored. His demotion to Triple-A should allow him to get more reps in an everyday role in the infield.