That resulted in a surgical procedure that kept Santos on the sidelines until early July, when he began a rehab assignment in the Minor Leagues. He was activated prior to Thursday night's game against the Angels and will assume a spot in middle relief.
"I was making progress with every inning I was throwing, as far as with my pitches," Santos said of his rehab. "It's just a matter of getting back into the flow of games and I'm hoping with each inning I throw, each game I'm in, I can speed that process up a little bit."
Injury problems have been an ongoing concern for Santos, who has thrown just 9 1/3 innings since coming over from the White Sox in a trade at the 2011 Winter Meetings. Last year, a shoulder injury ended his season after just five games.
Santos was acquired by general manager Alex Anthopoulos to become the Blue Jays' closer after he saved 30 games for Chicago in 2011. He lost that job to Casey Janssen because of the prolonged injury and was expected to serve as the eighth-inning setup man in 2013.
That also has changed because of the emergence of All-Stars Steve Delabar and Brett Cecil, but there are still plenty of innings to go around. Santos admitted he thought about the depth of Toronto's bullpen on his way back to the Majors but said it couldn't impact his outlook.
"You can't help but wonder, but the smart guy inside says not to really think about it because it's not in my control," Santos said when asked if he doubted his future spot on the Blue Jays. "All I can control is how I'm feeling and trying to get back healthy.
"It's hard to get a year and a half of work in just nine innings. I know it's going to be a process. I'd like it to be as smooth and in rhythm as I was when coming here, I know those expectations are a little high so all I can do is just work pitch by pitch. I'm taking that mindset for the rest of the season and hopefully it works."
Toronto hasn't been exposed to much of Santos over the past two years but he still has the potential to become one of the elite bullpen arms in the American League. He has an upper-90s velocity fastball with a devastating slider that generates a lot of swings and misses.
The 30-year-old Santos pitched six innings for Triple-A Buffalo during his recent rehab stint, but the real test comes now that he will be matched up against big league hitters.
"It's just a little different because down in the Minor Leagues they're swinging at everything," Santos said. "So it was hard, when you want to get ahead with a first-pitch fastball and kind of work on things, you can't really work an at-bat, because they're pretty much swinging at every pitch and putting the ball in play. So that was difficult but once you get past that, I was focusing more on my pitches than what they were doing."