Pittsburgh Steelers backup tailback Jerome Bettis, filling in for previously injured Duce Staley, left last night's 17-10 loss to the Washington Redskins with a strained right calf. Bettis was injured without being hit and will have an MRI this morning to determine the extent of the injury. Staley predicted his own return for the Sept. 11 opener, but Cowher said last week the Steelers want to bring Staley along more slowly after Aug. 8 surgery to repair his lateral meniscus. Third string back Willie Parker, filling in for the injured Bettis, was solid gaining 112 yards on 11 carries.