"He'll be back [on Sunday]," Cubs manager Dale Sveum said on Saturday about Sweeney. "It'll be good to have him back."
Valbuena, who has been out since Aug. 3, may need a little more time. Kane County's season ends on Monday.
"I'd like to have him back as well," Sveum said.
Sweeney was batting .295 when he was injured, while Valbuena was hitting .225, but had hit nine home runs and driven in 31.
The Cubs also may add a left-handed pitcher to the bullpen. James Russell has handled those duties by himself for the majority of the season.
September will be a key month to evaluate the Cubs players.
"I think the last month is priceless for some guys, especially some guys who had a tough struggle or whatever," Sveum said. "Other guys are being evaluated for next year. The adage of it's not how you start, it's how you finish, it helps the winter a lot. You don't want a bad September and then sit on that for the winter."
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.