After going undrafted in the
2002 NFL draft, Mustard was signed by the
Omaha Beef of the
National Indoor Football League as a
free agent. Mustard started 13 games for the Beef, 10 at wide receiver and three at guard. On December 3, 2002, Mustard signed with the
Cleveland Browns practice squad, then signed a futures contract with the Browns on January 8, 2003. In a 2008 interview, Mustard recalled his ever-changing employment status in Cleveland: "My career was so iffy, I lived in a hotel there for almost two years." Playing in 12 games with two starts, Mustard had a career high 62 receiving yards on five catches in
2007. In
2008, his final pro football season, Mustard played in eight games off the bench, his only statistic being a 17-yard kickoff return. ==Post-football career==