Guzman (back) is slated to begin a rehab assignment at Triple-A Oklahoma City on Thursday, Jose de Jesus Ortiz of the Houston Chronicle reports. Guzman first came down with back spasms on Aug. 1, spurring a prompt placement on the disabled list. When he's healthy enough to return, though, he'll play second fiddle to Jonathan Singleton at first base, with the ability to take on left field as well.