The hard throwing righty is now eligible to be claimed by any other team, but if he clears waivers, there's still a chance Santos would remain in the organization.
"He threw some strikes, but they weren't good strikes," manager John Gibbons said. "At the start of the season, he was pretty good for us. Last September, he was really good. But other than that, he's had a tough go. Relievers have tough lives. We needed a guy and he has been scuffling."
Even if Santos clears waivers, he's likely thrown his last pitch for the Blue Jays. There's a $6 million club option on his contract for next season that is all but guaranteed of being bought out at the end of the year for $750,000.
Right-hander Chad Jenkins was recalled from Triple-A Buffalo to take Santos' spot on the 25-man roster. Jenkins has worked exclusively as a reliever for Toronto this year and has a 2.56 ERA in 21 appearances.
Santos, 31, is 7-12 with a 3.89 ERA in the Major Leagues. The right-hander posted 30 saves in 2011 with the White Sox and was acquired by the Blue Jays in a trade for Nestor Molina the following offseason. Santos has pitched in just 61 games for Toronto over three seasons.
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.