Sweeney (hamstring) went on a rehab assignment with the Arizona League Cubs on Friday, MLB.com's Carrie Muskat reports. Sweeney has been on the disabled list since Aug. 27, but is starting to work towards a return from the disabled list by joining the Arizona League team. He appears to be on track for a return from the disabled list as soon as he is first eligible on Sept. 11, but it's unclear how much playing time he will receive when he returns.