The Giants optioned Osich to Triple-A Sacramento on Friday, John Shea of the San Francisco Chronicle reports.
Osich was promoted from Triple-A on Tuesday and allowed two runs on three hits with two walks and a strikeout in his lone appearance this week. The 29-year-old has a 8.25 ERA and 2.25 WHIP over 12 innings this season, and was demoted to make room for the return of Mac Williamson (concussion) from the disabled list.