The Phillies placed Keller on the 15-day injured list Tuesday, retroactive to Sunday, with right forearm tendinitis.
Keller appears to have picked up his forearm injury following his last outing Saturday in Milwaukee, during which he gave up three earned runs in one inning out of the bullpen. He'll now spend at least the next couple of weeks on the shelf, and Max Lazar will come up from Triple-A Lehigh Valley to fill the vacancy in Philadelphia's bullpen.