After playing college football for the Rutgers Scarlet Knights, he was selected by the Detroit Lions in the fifth round of the 2001 NFL draft.
McMahon played at North Allegheny High School in Wexford, Pennsylvania,[1] where he became the starting quarterback during his senior year in 1996.
[3] While in high school, he was featured in an NFL Films Presents episode as a potential next premiere quarterback to originate from Western Pennsylvania.
McMahon began the 2001 season as the third-string quarterback behind starter Charlie Batch and backup Ty Detmer.
McMahon started the 2005 season as the third-string quarterback behind starter Donovan McNabb and backup Koy Detmer.
[21] With McNabb undergoing season-ending sports hernia surgery following a November 14 game against the Dallas Cowboys, McMahon took over the reins of the Eagles for the remainder of the season.
[22] McMahon was signed to a two-year contract by the Minnesota Vikings on March 23, 2006, a move which reunited him with then-Vikings head coach Brad Childress, who was previously the offensive coordinator in Philadelphia.
[23] McMahon lost a training camp battle for the third-string job with fellow quarterbacks Tarvaris Jackson and Brooks Bollinger.
His stint as a starter lasted only two games before being replaced by Damon Allen as the acting starting quarterback for the team.