CHICAGO -- The Chicago Cubs placed their best reliever, Brandon Kintzler, on the 10-day injured list Tuesday after the right-hander hurt his right pectoral against the Oakland Athletics the previous night.

"I don't think there's anything spectacularly wrong with him, but it's there," manager Joe Maddon said Tuesday. "The guy has been a rock for us. We want him to continue to be a rock for us. Why push it right now and find out we're wrong? It's a conservative route."

Kintzler has a 2.33 ERA in 49 appearances while stranding 79 percent of his inherited runners this season.

Maddon thinks the 35 year-old veteran injured himself on a pitch to Matt Olson in the eighth inning Monday when he came out of his delivery to "manufacture velocity or movement."

"That's what occurred," the manager said. "Whether it was knowingly or unknowingly on his part ... He's been probably our most consistent relief pitcher all year. To push it right now, we just didn't think it's wise."

In the corresponding roster move, the Cubs activated Pedro Strop from the injured list. The right-hander was struggling before being sidelined by a neck injury, so Maddon said he will try to avoid a high-leverage moment for his return.

"I don't think it's wise to put Pedro in at the end of the game," Maddon said of Strop, who has a 5.32 ERA in 32 appearance for the Cubs.