"I'll try to get him an opportunity," manager Dale Sveum said Thursday of Strop.
The switch is not a reflection of Gregg's performance. But Gregg will be a free agent after this season. Strop will be entering his first arbitration year.
"Kevin's done far and above the call of duty," Sveum said. "He's done one heck of a job. It's going to be an opportunity [for Strop]. We want to see what he does in that role. Kevin has been one of the better closers in all of baseball. God knows where we'd be without him."
Gregg is 32-for-37 in save opportunities with a 2.95 ERA, and he began the season 12-for-12 in saves. He was released by the Dodgers after Spring Training and signed a Minor League contract with the Cubs on April 5. Carlos Marmol began the season as the Cubs' closer, but he was replaced after the first week by Kyuji Fujikawa, who was eventually sidelined because of elbow problems and needed Tommy John surgery. Marmol was dealt to the Dodgers in July.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.