Buchholz will see Dr. James Andrews next week for a second opinion. It's not immediately clear when he'll return, but if the diagnosis is confirmed, the veteran will miss significant time, Chisholm adds.
The two-time All-Star was scratched from his start on May 10 with shoulder inflammation. At the time, Buchholz said he hoped to only miss one start.
The 34-year-old is 0-2 with a 6.57 ERA in five starts for Toronto this season. He signed a one-year deal with the Blue Jays in late February after a strong campaign - albeit one cut short by injury - with the Arizona Diamondbacks in 2018 that saw him author a 2.01 ERA in 98 1/3 innings.
The Blue Jays' starting rotation has suffered a rash of injuries. Matt Shoemaker (knee) is out for the season, Clayton Richard (knee) hasn't thrown a pitch in the majors in 2019 but is currently on a rehab stint in Triple-A, and Aaron Sanchez left Friday's game with another blister issue.