The Giants optioned Lopez to Triple-A Sacramento on Tuesday, Shayna Rubin of the San Francisco Chronicle reports.
The Giants acquired Lopez from Toronto during the offseason, and he will return to the minors to begin the season after going 5-for-21 with a homer and nine RBI during the spring. Lopez has three hits in five career MLB plate appearances, though he will have to prove he can perform consistently in Triple-A before he can secure a big-league role.