Mets manager Mickey Callaway said deGrom's elbow was "barking" after playing catch Friday, according to Gelbs.
Although Callaway downplayed the severity of the ailment at the time, the Mets will place deGrom on the injured list retroactive to April 16, according to Anthony DiComo of MLB.com. Team general manager Brodie Van Wagenen described the injury as "mild soreness" and called the MRI "an abundance of caution," according to DiComo.
The Mets are set to begin a three-game series against the St. Louis Cardinals at Busch Stadium on Friday. The reigning NL Cy Young winner was set to pitch in the second game of the set on Saturday after having his original scheduled start pushed back from Friday due to an illness. A replacement starter hasn't yet been named.
DeGrom, who underwent Tommy John surgery in 2010, is coming off a remarkable season during which he authored a 1.70 ERA and 1.99 FIP over 217 innings pitched in 2018.
In his first two starts of the 2019 campaign, the 30-year-old picked up where he left off, striking out 24 batters over 13 shutout innings. However, the subsequent pair of games were decidedly less dominant for deGrom, as he allowed nine runs - all earned - on 13 hits, including five homers and five walks.
Last month, the Mets and deGrom reached an agreement on a five-year, $137.5-million extension, keeping the club's ace in Queens through 2023. The veteran pitcher was set to hit free agency following the 2020 season.