I dont think your giving duck enough credit for his speed. The top rated RB at the moment(LeSean McCoy runs a 4.4.The #2 RB(Chris Wells) runs a 4.5. The #3 RB(James Aldridge) runs a 4.45. Shall i go on or is that enough. If u dont beleive me heres the web site http://www.Unapproved Website/viewrank.asp?ra_key=1146&Year=2006
P.S.- Duck runs a 4.5