DETROIT -- As expected, the Tigers placed Daniel Norris on the 15-day disabled list Thursday with a right oblique strain, continuing the revolving-door effect on their pitching staff.
Not expected was another roster move, which put their rotation into further disarray. Anibal Sanchez, who leads the Tigers in innings pitched, but also leads the Majors in home runs allowed, joined Norris on the 15-day DL with a strain in his right rotator cuff.
Norris is expected miss at least two weeks, possibly longer, manager Brad Ausmus said. For reference, former Tigers reliever Joakim Soria missed a month with an oblique strain.
The timetable for Sanchez depends on what doctors see from his tests, but there's optimism it shouldn't be a lengthy injury.
"We don't think it'll go beyond the [minimal 15-day] DL stint," Ausmus said.
Taking their place for now will be relievers Guido Knudson and Jose Valdez. For the 26-year-old Knudson, whose contract was purchased from Triple-A Toledo, it will be his first Major League stint after five Minor League seasons.
The Tigers acquired left-hander Randy Wolf from the Blue Jays on Thursday to fill one spot. He'll start Saturday against Texas, pushing Matt Boyd back to Sunday. They'll need one more addition Monday for a makeup game at Cincinnati.
"We've talked about a number of guys," Ausmus said.
The Tigers drafted Knudson in the 28th round out of the University of California, San Diego in 2011. While he posted consistently good numbers on his way up the system, he put up some of his strongest results this summer at Triple-A Toledo, where he took over the closer's role in late June and racked up 10 saves.
Knudson had a 1-2 record and a 2.52 ERA in 30 appearances, allowing 27 hits over 39 1/3 innings. While his 21 walks were a high total for the number of innings he pitched, so were his 40 strikeouts.
The 25-year-old Valdez gets his second callup in three weeks. He was recalled from Toledo on July 31 after the Joakim Soria trade, but he didn't retire a batter in his one appearance, allowing two runs on three hits (including a home run) and a walk. Valdez had a 4-4 record and a 3.44 ERA in 38 appearances with Toledo, having allowed 44 hits over 52 1/3 innings, with 33 walks and 40 strikeouts.
Norris strained his oblique in his fourth start for the Tigers on Wednesday night against the Cubs, leaving in the fifth inning with a 7-3 lead. He underwent an MRI exam Thursday in Detroit to determine the extent of the injury, but Ausmus knew fairly quickly it would require a DL stint.
Sanchez took a no-decision against the Cubs on Tuesday, leaving in the third inning following a lengthy rain delay. He's 10-10 with a 4.99 ERA in 25 starts, but has posted only one quality start in the past two months, covering 10 starts. Sanchez has said all season that he's baffled by the rash of home runs -- his 29 allowed are already nine more than his previous career high -- but supposedly didn't mention any discomfort to the team until after his latest outing despite it bothering him at times over the past couple of months.
"I didn't know if he was getting tired," Ausmus said. "Especially his last start, the velocity came down a little bit, which is always concerning. I wasn't aware of any particular issue, but it doesn't shock me."
Jason Beck is a reporter for MLB.com. Read Beck's Blog and follow him on Twitter @beckjason. This story was not subject to the approval of Major League Baseball or its clubs.