Middlebrooks was named First-Team All-State as a senior at Homestead High School in Homestead, Florida. He played college football for the Minnesota Golden Gophers. In 1999, he was named Second-Team All-Big Ten. In 2000, he was named First-Team All-Big Ten Conference, but missed the final four games of the season with a fractured ankle. Prior to the 2001 NFL Draft, he was regarded as the best man-coverage player in the Big Ten, with speculation that he would be drafted in the first round, despite his recent injury.
Middlebrooks signed as a free agent with the Argonauts on April 28, 2008. He was named defensive player of Week One of the 2008 CFL season with nine tackles and an interception of a long pass from Winnipeg's Kevin Glenn near the end of the fourth quarter.
On June 1, 2011, Middlebrooks announced his retirement after sustaining a serious neck injury he received nearing the end of the 2010 CFL season.