"He came in on the off-day and played a little catch and started feeling it a little bit," Mets manager Mickey Callaway said before Friday night's game at St. Louis. "We're not sure what it is."
The 30-year-old deGrom, who had been scheduled to pitch Saturday, is coming off two shaky starts. He is 2-2 with a 3.68 ERA in four games this season.
DeGrom will go on the injured list retroactive to Tuesday, the team said.
"We don't know if it's just from general fatigue so we're being overly cautious at this point and making sure we take care of him," Callaway said. "We've got 90 percent of the season left and we feel no reason to really push him too much at this point."
Callaway said deGrom's elbow was "barking." DeGrom had Tommy John surgery in 2010.
DeGrom was dominant while pitching 13 scoreless innings and striking out 24 in his first two outings, extending his streak to a record-tying 26 straight quality starts. But he lost his last two starts while allowing a total of nine runs on 13 hits - including five homers - and five walks in nine innings.
DeGrom posted a 1.70 ERA in 32 starts last season. He signed a $137.5 million, five-year contract in March, right before opening day.
Mets general manager Brodie Van Wagenen said deGrom had been recently slowed by strep throat.
"Additionally, Jacob experienced some mild soreness in his throwing arm over the last 24 hours. His arm felt significantly better following treatment with our health and performance staff today," he said. "Even so, Jacob will be evaluated by our medical team in New York on Monday in the abundance of caution."
Van Wagenen said it was anticipated deGrom could return April 26 when the Mets start a series at home against Milwaukee.
The Mets have not announced a starter for Saturday. Callaway did confirm that Noah Syndergaard will pitch as scheduled on Sunday with Steven Matz taking his regularly scheduled turn Monday against Philadelphia.
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