According to Joel Sherman of the New York Post, Syndergaard left Saturday night's game against the St. Louis Cardinals because of a right hamstring strain. On Sunday, the Mets placed Syndergaard on the injured list.
The right-hander was charged with five runs (four earned) in six-plus innings of work, striking out five while walking two. He exited in the middle of an at-bat against Cardinals right fielder Jose Martinez.
The 26-year-old has had problems staying on the field since the start of 2017, making just 32 starts over the past two seasons.
New York's ace made 11 starts over the first two months in 2018 before landing on the injured list with a strained ligament in his right index finger.
He returned to make two starts in July before going back on the 10-day IL after contracting hand, foot and mouth disease working at a youth camp during the All-Star break.
When Syndergaard was healthy in 2018, he remained effective with a 3.03 ERA and 155 strikeouts in 154.1 innings over 25 starts. The right-hander started slow this season with a 4.45 ERA despite having 93 strikeouts in 95 innings.
The Mets remade their roster this offseason, acquiring Robinson Cano and Edwin Diaz in a trade with the Seattle Mariners and signing Jed Lowrie to play third base.
Starting pitching remains the key to New York's success, led by Syndergaard and reigning NL Cy Young winner Jacob deGrom. Syndergaard's absence will push Zack Wheeler and Wilmer Font into more prominent roles in the rotation.