The return likely won't happen for at least a couple of weeks because Stroman isn't eligible to be called up for 10 days, unless there's an injury on the 25-man roster.
"He's going to go down there and start and we'll kind of see how this plays out in the next few weeks," Blue Jays manager John Gibbons said.
Toronto did not announce a corresponding roster move with Stroman's demotion. One possibility would see right-hander Liam Hendriks recalled from Buffalo to pitch out of the bullpen before entering the starting rotation on May 24 vs Oakland.
The Blue Jays temporarily moved to a four-man rotation with an off-day coming on Monday. That will change for the game against the A's, and Hendriks is the early favorite for the role. Blue Jays general manager Alex Anthopoulos recently watched Hendriks pitch in Buffalo, where the 25-year-old has a 1.48 ERA in nine games.
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.