He played college football for the Oklahoma State Cowboys and was selected by the Denver Broncos in the fifth round of the 2010 NFL draft.

Cox attended University High School in Waco, Texas, where he was a standout on both sides of the football.

Also a standout track & field athlete, Cox was one of the state's top performers in both sprints and jumps.

Cox entered his senior season just 110 kickoff return yards short of the Big 12 career record.

[4][5] His draft stock dropped after a slow 40-yard dash at the NFL Combine, but he was able to improve his workout numbers at OSU's Pro Day.

[12] Cox was released by the 49ers on November 12, 2013 to make room on the active roster for returning linebacker Nick Moody.

[16] On January 18, 2017, Cox signed with the Seahawks after an injury suffered by DeShawn Shead following the 36–20 loss to the Atlanta Falcons in the divisional round of the 2016 playoffs.

[19] He was also suspended from the Cotton Bowl in his senior season by head coach Mike Gundy for violating the team curfew rule.

[21] However, on March 2, 2012, Cox was found not guilty of sexual assault charges in Douglas County, Colorado criminal court.