Gsellman will join the Mets rotation while Jon Niese is on the disabled list, Marc Carig of Newsday reports.
Gsellman pitched 3.1 innings with the Mets on Tuesday, the first MLB innings of his career. In said game, he allowed two hits and three walks, but didn't allow any runs. Unfortunately, his outings at Triple-A Las Vegas haven't gone as well. After nine starts at the Triple-A level, Gsellman has a 5.73 ERA, 1.48 WHIP and 40:16 K:BB in 48.2 innings. Now that he's in the big club's rotation, his next start is expected to be Sunday against the Phillies.