Osuna felt some discomfort on the right side of his lower back. It's being described as a cramp, and at the moment it doesn't sound like anything that will need to be checked out by an MRI.
"Well, I felt a cramp in the first pitch of the last inning, like a cramp in my lower back on the right side," Osuna said after picking up his third save of the season. "Nothing serious, just that ... I didn't feel like I had to get out of the game. I could pitch, and that's what I did."
Osuna said that he would be ready to pitch on Monday in Chicago, but the Blue Jays likely will give him at least one day of rest. That has more to do with the fact he threw 21 pitches and tossed 1 1/3 innings vs. Detroit than the injury, but it's something that will have to be closely monitored.
The 20-year-old closer admitted that he likely will feel sore within the next 24 hours and that's not an encouraging sign, but if it's just a cramping issue, it shouldn't be long before Osuna is back to 100 percent.
"A little bit tight, a little bit tight," Osuna said after the game when asked how it felt. "I think it's going to be sore tomorrow. I don't know why, but that's what I think."
The Blue Jays can ill afford to lose Osuna for any extended period of time. He has been a stabilizing force with a 2.13 ERA in an otherwise struggling bullpen.
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, follow him on Twitter @gregorMLB and Facebook, and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.