The left-hander began his comeback over the offseason and was pitching in the Venezuelan Winter League, but was shut down with shoulder stiffness.
The 35-year old went 6-9 with a 4.85 ERA in 2012 with the Mets and is 139-78 with a 3.20 ERA across 12 Major League seasons.
The Blue Jays are looking at Santana as a starter, but it's unclear if he will be fully healthy by the time Opening Day rolls around.
If Santana is indeed healthy, he'll be competing with Marco Estrada and Daniel Norris for the fifth spot in the Blue Jays' rotation.
William Boor is a reporter for MLB.com. Follow him on Twitter at @wboor. This story was not subject to the approval of Major League Baseball or its clubs.