He is having an MRI, according to Mets manager Luis Rojas, with results expected early Tuesday evening.
“[deGrom] let us know earlier today that he had some tightness on his right side,” Rojas said. “I saw him before coming to the field and he was stretching, trying to feel his right side a little bit, and that’s when we started discussing whether he was going to start or not.”
Right-handed reliever Miguel Castro will start in deGrom’s place against the Cardinals.
DeGrom is 2-2 with an MLB-best 0.51 ERA and 59 strikeouts through five starts. He was recently named NL Pitcher of the Month for April.