Cain left Saturday's game against the Cardinals with groin tightness, Tom Haudricourt of the Milwaukee Journal Sentinel reports.
It's the second time in three days that Cain has exited a game prematurely, having left Thursday's contest with a hamstring cramp. The severity of the groin issue is not yet clear, but even if the injury is a minor one, the Brewers could elect to rest Cain on Sunday, as the team has a scheduled off day Monday, allowing the outfielder to have two full days to heal.