The Blue Jays have optioned right-handed pitcher Chad Jenkins to the Triple-A Buffalo Bisons to make room on the 25-man roster for left-hander Brad Mills.
Toronto claimed Mills off waivers from the Oakland Athletics on Thursday.
The 29-year-old Mills started three games for Oakland this season, posting a 1-1 record with a 4.41 earned-run average.
Originally drafted in the fourth round in 2007 by the Blue Jays, the six-foot, 188-pound pitcher has a career record of 4-4 in 18 games (13 starts) with a 6.98 ERA with Toronto, the Los Angeles Angels and Oakland.
Jenkins, 26, has appeared in 15 games for the Jays so far in 2014, posting an 0-1 record with a 3.72 ERA and a 1.24 WHIP.