Santos was placed on the DL on May 12 with a strained right elbow. He made two rehabilitation appearances for Double-A New Hampshire, allowing four runs in two innings.
Before the injury, Santos was 0-2 with a 9.00 ERA and five saves in 14 appearances.
To clear a roster space for Santos, the Blue Jays on Saturday optioned outfielder Darin Mastroianni to Triple-A Buffalo.
Mastroianni, who was recalled from Buffalo on Thursday, is 0 for 13 this season with Minnesota and Toronto.