Perez isn't starting Wednesday against the Cubs due to a right shoulder injury, Mandy Bell of MLB.com reports.
The 31-year-old spent time on the injured list earlier in the season with a right shoulder strain, and he's apparently still dealing with some of the effects of that injury. The initial injury presented more of a hindrance on throws, but the current issue is presenting problems on swings. Temporary manager Sandy Alomar Jr. said Perez will need to find a way to work through the discomfort, or he'll end up receiving a couple days off to recover. The team hopes he'll be ready to rejoin the lineup Thursday in Detroit.