Blue Jays manager Charlie Montoyo said Tuesday that Pearson (illness) has been diagnosed with mononucleosis and will be out "a while," Ben Nicholson-Smith of Sportsnet.ca reports.

EDGE Analysis

Pearson was already on track to miss out on a spot in the Blue Jays' Opening Day bullpen after an unspecified ailment had kept him from working out with the team for the past few days, and he looks like he'll be sidelined for the first few weeks of the season now that he's received a diagnosis for his illness. The Blue Jays are expected to formally place Pearson on the injured list at some point before the weekend. Since Toronto had planned to have Pearson stretch out for starting duty in the spring, he could prepare for a rotation role with Triple-A Buffalo once he's cleared to begin a minor-league rehab assignment. Before he even resumes throwing, however, Pearson will turn his focus on resting up and attempting to shake off an illness that can often carry a volatile recovery timeline.