Marlins pitcher Kevin Slowey will be out four to six weeks due to a strained right forearm muscle an MRI revealed on Monday.
Slowey felt discomfort while warming up in the bullpen during Saturday's game against Pittsburgh.
With the projected timetable for a return and the Marlins out of the playoff picture, Slowey could miss the rest of the season.
"As much as I want to figure that out right now, I know I'm just best off taking it one day at a time," Slowey said.
Slowey is 3-6 with a 4.11 ERA in 20 games, making 14 starts in his first year with the Marlins.