Lopez was sent to Triple-A Colorado Springs on Friday, Tom Haudricourt of the Milwaukee Journal Sentinel reports.
Lopez will head back to the minors after appearing in six games for the Brewers, posting a 4.35 ERA and 1.65 WHIP with eight strikeouts and six walks across 10.1 innings. Adrian Houser was recalled from Triple-A to replace the 25-year-old right-hander.