The Mets announced that Syndergaard was examined Tuesday back in New York after experiencing soreness in his right index finger. The move to the DL is retroactive to May 26.
"He threw a side yesterday, and that's when he started noticing it, that [it] was sore," New York manager Mickey Callaway said Tuesday in Atlanta. "He had some bruising at the base of his wrist, so we just said that he needs to get that checked out."
Callaway added that Syndergaard had "a little" soreness after his last start and that the pitcher would wear a splint on his finger to keep it immobilized.
Callaway didn't seem to believe Syndergaard would miss much time.
"Right now, the goal is to rest it a couple of days and give him a bullpen this weekend," Callaway said. "After that, he should be all good."
The DL stint for Syndergaard is the latest bit of bad news for the injury-plagued Mets, who already are without slugger Yoenis Cespedes, third baseman Todd Frazier, center fielder Juan Lagares, starting catcher Travis d'Arnaud, infielder Wilmer Flores and relievers AJ Ramos and Anthony Swarzak.
Syndergaard had been scheduled to pitch Wednesday at the Atlanta Braves. The Mets will start Jason Vargas instead after just three days of rest -- and after Vargas lasted only three innings in his previous appearance on Saturday. Seth Lugo will start on Thursday.
Right-hander Gerson Bautista, who was called up from Triple-A Las Vegas to serve as an extra player for Monday's doubleheader in Atlanta, will remain with the team.
Syndergaard, 25, has pitched well this season after missing most of 2017 with a lat injury, going 4-1 with a 3.06 ERA and 76 strikeouts over 64⅔ innings in 11 starts.
On Tuesday, all seemed to be going smoothly for the Mets at SunTrust Park after New York grabbed a 4-0 lead against the Braves.
But then, after Steven Matz started to warm up before the bottom of the fourth, the training staff was summoned to the mound. He was removed from the game because of discomfort in the middle finger of his left hand.
Matz's X-rays were negative, and there was no word on how long he would be out beyond Tuesday's start, if at all.
The Mets lost the game 7-6.
ESPN's Bradford Doolittle and The Associated Press contributed to this report.