The Mets announced the roster move Sunday, one day after Syndergaard suffered the injury during his start against the St. Louis Cardinals.
Syndergaard was scheduled to undergo an MRI on Sunday morning. The Mets have not disclosed a timeline for how long the hard-throwing right-hander will be sidelined.
New York activated second baseman Robinson Cano from the 10-day IL in a corresponding roster move. Cano, who has been plagued by a left quadriceps injury for the past month, will bat fifth Sunday against the Cardinals.
Syndergaard is 5-4 with a 4.55 ERA.