Hammer's contract was purchased from Triple-A Lehigh Valley on Saturday, Meghan Montemurro of The Athletic reports.
The 24-year-old reliever has a 1.61 ERA, 0.94 WHIP and 29 strikeouts in 22.1 innings across stops at Triple-A and Double-A. He takes the place of Pat Neshek, who landed on the injured list with a shoulder strain.