The Brewers hit Karstens hard, with five of six batters reaching base. Aramis Ramirez hit a two-run single and Corey Hart hit a two-run homer to give Milwaukee a 4-0 lead. Jonathan Lucroy followed with a single on Karstens' 20th pitch, prompting trainers to go to the mound and talk to the right-hander.
He walked back into the dugout and was replaced by right-hander Kyle McPherson, recalled from Triple-A Indianapolis earlier Friday.
Karstens was pitching for the first time since being removed due to a grain strain after seven innings in a 4-0 victory over Milwaukee last Saturday.