Fox was drafted in the 3rd round (80th overall) of the 2005 NFL Draft by the Minnesota Vikings. Fox fractured the radius bone in his left arm in training camp while tackling running back Mewelde Moore, during the first session in full gear, and was released on September 2, 2006.
On September 4, 2006, Fox was signed to the Philadelphia Eagles' practice squad, and was promoted to the 53-man roster on September 19. He was, however, released by the Eagles on October 4, and then re-signed to the practice squad the next day. On January 27, 2007, Fox was signed to a new contract by the Eagles.