Leon cleared waivers and was outrighted to Triple-A Buffalo, Gregor Chisholm of MLB.com reports.
Leon was designated for assignment Wednesday by the Blue Jays, Ben Nicholson-Smith of Sportsnet reports.
Leon was charged with the loss after serving up an eighth inning three-run homer to Steven Souza Jr. giving the Rays a 5-3 win.
Leon will open the season in the Blue Jays' bullpen, the Toronto Star reports.
Leon was traded to the Blue Jays on Tuesday for cash considerations.
The Athletics designated Leon for assignment Monday.
Leon was recalled from Triple-A Nashville on Tuesday.
Leon was optioned back to Triple-A Nashville on Friday.
Leon was optioned to Triple-A Nashville on Friday.
Leon was recalled from Triple-A Nashville on Thursday.