Peralta left Thursday's start against the Giants in the top of the third inning with the Brewers winning 3-0 and a runner on first base with zero outs, Adam McCalvy of MLB.com reports.
Andrew Baggarly of The Athletic noted that Peralta seemed to shorten up noticeably on his last pitch, suggesting that he likely suffered an arm or shoulder injury. Peralta had his start pushed back three days because his shoulder wasn't bouncing back as it should. He missed 10 weeks in the middle of the season with a strained right shoulder, and if he re-injured his shoulder, there's a chance he might not make it back this season. Peralta struck out three and walked two over two scoreless innings Thursday prior to his exit.