Lawrie suffered the injury when he was hit by a pitch during a game on May 31 while playing for Triple-A Las Vegas.
Initial X-rays did not reveal any fractures but when the swelling in his hand subsided a CAT scan discovered the damage.
"We took every precaution with every imaging available to us, so that we weren't overlooking something," Blue Jays manager John Farrell said. "The X-rays showed no fracture, he was X-rayed a second time, the bone scan showed no fractures, but yet the CAT scan did."
Lawrie was returned to the club's Minor League complex in Dunedin, Fla., to maintain his conditioning. He is not allowed to participate in any baseball-related activities for at least the next two weeks and likely won't return to Triple-A Las Vegas until the beginning of July.
The 21-year-old third baseman was hitting .354 with 15 home runs and 49 RBIs in 52 games this season. He also had 19 doubles and an impressive .415 on-base percentage while stealing 11 bases.
The latest development comes as a major blow to Lawrie, who was on the verge of being called up to big leagues at the time of his injury. General manager Alex Anthopoulous described the promotion as being "close" and it was expected he would debut in Baltimore on June 3.
"That's the one thing that is so uncontrollable, you just try to prepare the best you can through depth and other options," Farrell said. "This is unfortunate considering how close he is and yet this is a setback.
"He'll have to definitely get back into games once he is able to resume baseball activity and build back up to seeing live pitching again."