"It was just affecting me on all pitches," Syndergaard said. "I haven't had it in a long time. I had it when I was going through the minor leagues with the Blue Jays, but kind of a rare occurrence."
Syndergaard's next start will be pushed back to Sunday because of the blister. Robert Gsellman, who pitched the ninth inning Monday, will get the start Saturday in the Mets' fifth game.
Syndergaard said he picked up the blister in the second inning, then it opened in the fifth, and he battled through the sixth before leaving the game.
"It's not very big. He had it, and it popped during the inning," Mets manager Terry Collins said. "These guys, that's a very common thing. They'll dry it out the next couple days. He'll be ready."