Coach Shanahan Makes Scientific Breakthrough?

Reports coming out of the Washington Redskins training camp state that the 'Skins have made an offer to elderly and fragile running back Brian Westbrook. With Clinton Portis, Larry Johnson and "Reasonably Fast" Willie Parker already on the roster, this makes the Washington backfield the NFL equivalent of the Rolling Stones in that their former greatness can't be denied but they really haven't had any great new stuff in years.
All of these signings have led to widespread speculation that Coach Shanahan has somehow developed a time machine because most agree that it would be the only plausible explanation for this running back corps. Shanahan has denied the rumours but did state that he would trade troublesome but talented DT Albert Haynesworth for a used flux capacitor in good condition.