The Padres placed Cosgrove on the 15-day injured list Friday with a left hamstring strain.
Cosgrove has been one of the most reliable options out of the bullpen for San Diego all season with just one earned run through 17 innings. However, he will now be shelved for at least 15 days. He will trade places with Nabil Crismatt (hip), who was reinstated from the 15-day IL in a corresponding move.