According to Andy Martino of SNY, Mets reliever Robert Gsellman has been diagnosed with a partial lat tear.

Gsellman went on the injured list on August 17 with tightness in his triceps. It turned out to be worse than just tightness, as Gsellman has a partial tear and will have to miss a fairly significant chunk of time. A timetable has not been announced yet, but given the timing and severity of the injury, it is unlikely that Gsellman will pitch again this season.

Gsellman has been healthy all year up until this point. He has appeared in 52 games, contributing with up-and-down results. He had been pitching better as of late, with a 3.57 ERA in 13 games since the All-Star break. Overall, he’s pitched to a 4.66 ERA.

The Mets are now down a reliever without Gsellman, hurting their already weak bullpen depth. They now will likely have to make do without him for the rest of the season.