Cubs activated RHP Pedro Strop from the 15-day disabled list.
Cubs placed RHP Pedro Strop on the 15-day disabled list with a moderate left groin strain.
Pedro Strop will undergo an MRI Wednesday to determine the severity of a groin injury.
Pedro Strop left Tuesday's game against the White Sox with an apparent injury.
Cubs manager Rick Renteria said Thursday that he does not have a designated closer at this point.
Pedro Strop gave up four runs in the top of the ninth inning Wednesday as the Cubs fell to the Diamondbacks.
Pedro Strop closed out the Cubs' 5-1 win on Monday, pitching a hitless ninth against the Diamondbacks.
Pedro Strop picked up a save Thursday in the Cubs' 3-2 defeat of the Pirates at Pittsburgh's PNC Park.
Pedro Strop pitched a perfect eighth in Wednesday's 7-5 loss to the Rockies.
Cubs avoided arbitration with RHP Pedro Strop by agreeing to a one-year $1.325 million contract.
Cubs pitching coach Chris Bosio suggested Pedro Strop and Hector Rondon could compete for the closer's job.
Cubs team president Theo Epstein indicated over the weekend that they have "guys that could close" already on the roster, likely referring to Pedro Strop.
Pedro Strop earned his first save of the season Saturday in the Cubs' victory versus the Braves.
Pedro Strop will serve as the Cubs' closer for the remainder of the 2013 regular season.