Raley, 24, was 5-4 with a 4.92 ERA in 13 appearances (12 starts) with Iowa. He made his big league debut last August, and was 1-2 with an 8.14 ERA in five starts.
"Right now, obviously, our bullpen is a little short, and we have some length there [with Raley] if anything happened," Sveum said.
Late Tuesday, the Cubs acquired reliever Henry Rodriguez from the Nationals for Minor League pitcher Ian Dickson. Rodriguez has not joined the Cubs yet.
"I don't think he's thrown in 10 days," Sveum said of Rodriguez. "We have some time to let him throw and see where we're at in a couple days."
Rodriguez, 26, had a 4.00 ERA in 17 relief appearances with the Nationals before he was designated for assignment on June 4.
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.