A day after Luis Rojas said David Peterson was good to go for Tuesday's start, Peterson was placed on the 10-day IL (retroactive to Aug. 14) due to left shoulder fatigue.
Rojas said before Tuesday's game that Peterson woke up with his shoulder "feeling weird," leading the team to scratch him from his start and place him on the IL.
Next steps regarding Peterson, including whether he'll undergo an MRI, are not yet known, according to Rojas.
Corey Oswalt, who was recalled from the alternate training site, will start on Tuesday in place of Peterson.
The Mets also optioned Franklyn Kilome to the alternate site and recalled Drew Smith.
Peterson, who left his last start after just 74 pitches due to shoulder soreness, recently threw a side session and had been classified as ready for Tuesday's start.
Peterson said after leaving Thursday's game that he wasn't at all concerned about the shoulder issue, which he said was common and general.
Wacha was set to throw a simulated game on Tuesday at the Mets' alternate training site in Brooklyn.
Rojas reiterated Tuesday that there hasn't been a decision made regarding whether the struggling Steven Matz would make his next start, scheduled for Thursday. But it doesn't seem the Mets have any choice at this point but to give the ball to him.