Per Meghan Montemurro of the News Journal, Buchholz's surgery repaired a torn flexor tendon in his right forearm, and he has an estimated recovery time of four to six months.
The Phillies acquired Buchholz from the Boston Red Sox during the offseason, and he was a mess through two starts with 16 hits and 10 runs allowed in 7.1 innings.
With Buchholz on the shelf, the Phillies recalled Zach Eflin from Triple-A to take his spot in the rotation. They also have Jeremy Hellickson, Jerad Eickhoff, Vince Velasquez and Aaron Nola to fill out the top four spots.
If Buchholz needs just four months to recover, the earliest he would be ready to return to the rotation is mid-August. If he needs a full six months, his 2017 season will be over, barring a deep playoff run by the Phillies.