Moyer, who was signed to a Minor League contract on Monday, is expected to make two starts for the 51s. After that, the Blue Jays will decide to either promote him to the Major Leagues or likely grant his release.
"This is an agreement that I think we'll come to a decision one way or the other pretty quick," Blue Jays manager John Farrell said.
"I think at that point, there's no guarantees. But we want a two-start look and then determine, 'Is he an improvement in our rotation?'"
The 49-year-old Moyer began the season with Colorado and went 2-5 with a 5.70 ERA in 10 starts before he was designated for assignment. Moyer then joined the Orioles' organization, but he was released after not being promoted to the Major Leagues.
Moyer's signing comes at a time when the Blue Jays starting rotation has been devastated by injuries. Right-handers Brandon Morrow, Kyle Drabek and Drew Hutchison are currently on the 15-day disabled list while Henderson Alvarez was forced to leave Monday night's game in Boston because of soreness in his right elbow.
Moyer, who missed all of last season because of Tommy John surgery, is 269-209 with a 4.25 ERA in 25 seasons at the big league level.