 He reportedly held out for a contract extension and never reported to Buffalo's training camp that year.On July 29, 2007, the Buffalo Bills traded Walker's rights to the Chicago Bears in exchange for an undisclosed draft pick in 2008 (the Bears were in need of a defensive tackle after having waived troubled defensive lineman Tank Johnson in the 2007 offseason).On April 28, 2008, he signed with the Carolina Panthers.