Ruf (knee) will begin a minor-league rehab assignment Tuesday with Triple-A Nashville, Adam McCalvy of MLB.com reports.
Ruf has been sidelined since early June due to a non-displaced fracture in his right kneecap, so he'll probably need several rehab games to get back up to speed. The 37-year-old holds a weak .224/.333/.286 batting line in 57 major-league plate appearances this season between San Francisco and Milwaukee.