"It's a weird time to designate somebody, Sept. 8," Sveum said. "It's an unfortunate thing, but it's part of the business."
Baker has been rehabbing all season from Tommy John surgery on his right elbow, which he had in April 2012.
• Right-hander Daniel Bard, whom the Cubs claimed off waivers from the Red Sox, threw a second bullpen on Sunday. There is no timetable for him to get into a game, and he may not appear in the Cubs' remaining 20 games.
"It'd be nice to see, but it's his timetable and we'll evaluate and we'll find out how he's doing and how he's feeling," Sveum said.
Bard was sidelined most of the season with a strained abdominal muscle and struggled with his consistency.
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.