ST. LOUIS -- New York Mets ace Jacob deGrom was scratched from Tuesday night's scheduled start against St. Louis because he was having trouble getting loose as he started to stretch ahead of his outing.
Mets manager Luis Rojas said deGrom had a scan that showed inflammation of the latissimus dorsi muscle, a back muscle that connects the upper arm to the spine and the hip.
DeGrom won't throw for a few days.
"And then he's going to be able to throw, maybe throw a side, and then that will determine when his next start is going to be," Rojas said.
Rojas said he learned of the issue about eight hours before the Mets' scheduled game against the Cardinals, which later was rained out and rescheduled as part of a single-admission doubleheader Wednesday.
"It's a positive that it came back that it's an inflammation only. It's a few days off from throwing per the doctor's recommendation," Rojas said. "He's optimistic, too, about what's next after the two days off."
Before a scan, Rojas described the ailment as tightness.
"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's going to start or not," the manager said.
Rojas said the issue was not evident before Tuesday.
DeGrom, a two-time NL Cy Young Award winner, has been baseball's most dominant pitcher this season, with a major-league-best 0.51 ERA in five starts. He has 59 strikeouts in 35 innings with just four walks. Still, he is just 2-2 as New York continues to have trouble scoring runs for him.
The 32-year-old right-hander has reached 100 mph on 46 of 473 pitches this season and lowered his career ERA to 2.55, overtaking Hall of Famer Tom Seaver (2.57) as the Mets' career leader.
Marcus Stroman will start the doubleheader opener, and Rojas was not sure who would start the second game. Right-hander Jordan Yamamoto, recalled from Triple-A Syracuse on Tuesday, was a possibility.
Miguel Castro, normally a reliever, had been slated to start in deGrom's place Tuesday. The game was delayed at the outset and called after a 38-minute wait.
Right-hander Sean Reid-Foley was optioned to Syracuse.
The Associated Press contributed to this report.