Lopez was optioned to Triple-A Colorado Springs on Thursday.
Lopez will head back to the minors in order to open up a roster spot for Boone Logan (triceps), who was activated from the disabled list in a corresponding move. The 25-year-old allowed three runs across four innings (two appearances) during his most recent stint with the big club, bringing his ERA up to 5.14 through seven innings on the season. Lopez will continue to bounce between the majors and minors as bullpen help is needed.