Mike Shanahan: Redskins’ starting running back is a secret

Redskins coach Mike Shanahan knows who his starting running back is going to be this season. But he isn’t telling. Shanahan said at his press conference today that he has a first choice among the three running backs on his roster (2011 fourth-round pick Roy Helu, 2011 sixth-round pick Evan Royster and 2012 sixth-round pick…