Santos was placed on the 15-day disabled list on Sunday for precautionary reasons and was then sent to be examined by Dr. Lewis Yocum in southern California.
The test results did not reveal any structural damage, but he was told not to throw for the next two weeks. The lack of activity during that time means Santos will have to go through rehab once he is given the green light and should miss at least a month.
"Ten to 14 days of no throw, and as we've used the typical rule of thumb, it's going to be at least the same number of days to get back to where he left off," Blue Jays manager John Farrell said. "That's going to take us right up to, probably, a four-week period."
Santos first experienced the soreness while recording a save in Friday's victory over the Royals. The pain still lingered the following day and there was a fear that Santos may have suffered a serious injury.
The level of concern was greater than normal because Santos had not experienced that type of soreness since being converted to a pitcher in 2009. Those worries were quickly alleviated, but the club isn't going to take any chances with something as serious as a right shoulder.
"He felt nothing last year, he felt nothing at any time while he's been converted to a pitcher and yet it showed up in that one outing and that's why we were concerned," Farrell said.
"If he didn't have this in Spring Training, and he didn't have anything leading up to that, then all of a sudden in one outing you have that kind of inflammation. We were concerned to the point of not questioning it, putting him on the disabled list and having him evaluated totally."
Santos, who was acquired from the White Sox during theoffseason, is 2-for-4 in save opportunities this year. He is being temporarily replaced by veteran Francisco Cordero at the back end of Toronto's bullpen.