The team announced Wednesday that Taillon underwent flexor tendon repair surgery a day earlier in New York. During the procedure, doctors determined the pitcher also required surgery to repair the ulnar collateral ligament in the elbow.
The Pirates said Taillon is projected to return to full competition for the 2021 season.
"He was shocked when he heard the news, as were we," Pirates starter Trevor Williams told reporters. "But he's got a good head on his shoulders, and he's going to come out of this stronger than he was before. We're penciling him in for Comeback Player of the Year, 2021."
Taillon, 27, also had Tommy John surgery in April 2014 while playing in the minors. He missed the 2015 season due to a sports hernia before making his MLB debut in 2016.
Taillon was 2-3 with a 4.10 ERA in seven starts with the Pirates this season. The team shut him down for about two months after he felt pain in his right forearm following his last start May 1 against the Texas Rangers.
The right-hander began to throw in late June before experiencing pain again at the end of July.
Taillon is 29-24 with a 3.67 ERA and 419 strikeouts across 82 career starts.