Shoemaker suffered the injury during a rundown on Saturday against the Oakland Athletics. He was placed on the 10-day injured list Sunday with what was first diagnosed as a left knee sprain.
The 32-year-old, whose unfortunate injury history includes a skull fracture and accompanying hematoma after taking a line drive to the head in 2016, was in tears after learning of the ACL tear, according to Sportsnet's Hazel Mae.
"I know I seem pretty upset right now, which I am, but I’ve had bumps in the road before and I’m just going to fight through it," Shoemaker said, according to Ben Nicholson-Smith of Sportsnet. "That’s just who I am. It’s just really upsetting right now."
Shoemaker will visit with a doctor in Toronto to figure out his next steps.
"No, we don't know what we're going to do. We just found out. He had his MRI today and we just found out," Blue Jays manager Charlie Montoyo said of the team's next direction, according to Sportsnet. "Bad news, bad news. He was one of the best pitchers in baseball ... tough loss for us."
Shoemaker was signed to a one-year deal in December. He was off to a terrific start for the Blue Jays, authoring a 3-0 record with a 1.57 ERA in 28 2/3 innings.