Pillar was up with the bases loaded when he took a 94 mph pitch to the face from Braves pitcher Jacob Webb. Somehow, Pillar was able to get up and walk back to the dugout under his own power.
He offered an update on his condition hours after he was removed from the game.
"Thanks to everyone that has reached out! Scary moment but I’m doing fine!" he tweeted.
The Mets said Tuesday that Pillar suffered "multiple nasal fractures" and will meet with doctors in Atlanta to discuss what's next.
The moment definitely concerned those on the Mets and Braves.
"It was not an easy moment," Mets manager Luis Rojas said. "Definitely our prayers are with KP. ... It’s tough. You think about a player’s career. You think about a lot of things in the moment and you get emotional."
Braves players were clearly in distress when Pillar went down.
"That’s about as sickening a thing as you can see on the baseball field when a kid gets hit like that," Braves manager Brian Snitker said. "I keep that kid in my prayers and hope everything is OK."
New York would go on to win the game, 3-1.
The Associated Press contributed to this report.