Pedro Strop suffers setback; John Lackey OK after mound session

CHICAGO -- Cubs reliever Pedro Strop suffered a setback in his rehab from a knee injury as an MRI revealed the righty strained his right groin during workouts on Wednesday.

Strop originally was to be out four to six weeks after tearing the meniscus in his left knee last month, though the Cubs had thought he might be back on the shorter end of that diagnosis. Now the team says he'll be out a full six weeks with a mid-September return. It still gives Strop plenty of time to prepare for the postseason.

The Cubs got better news in the form of John Lackey, who threw off the Wrigley Field mound on Thursday as he readies for a return from the disabled list due to shoulder soreness.

"I feel fine," Lackey said afterward."I feel like I can pitch in a game."

If Lackey feels OK on Friday morning, he'll be slated to start Sunday's game against the San Francisco Giants.

There's also good news for setup man Hector Rondon (triceps), who is headed to Triple-A Iowa for rehab outings on Saturday and Monday before he's expected to be activated as well.

The Cubs called up some reinforcements as rosters expanded on Thursday. Reliever Joe Smith (hamstring) and outfielder Chris Coghlan (rib contusion) were technically activated from the disabled list, as both were on rehab assignments at Triple-A, and righty Jake Buchanan was called up along with them.

Buchanan, 26, was 12-8 with a 4.34 ERA in 24 appearances for Iowa including 22 starts. He gives the bullpen some "length," as manager Joe Maddon has used his top relievers often during the Cubs' 22-6 August run.

"When you're winning often, you're going to use up a lot of good bullpen," Maddon said Thursday. "It's part of the way this thing flows."

Lackey is expected to be a playoff starter for the Cubs while Strop and Rondon are their seventh- and eighth-inning bullpen arms in front of closer Aroldis Chapman.