He signed his first NFL contract with the Vikings after spending the 2014 season with the Arizona Rattlers of the Arena Football League (AFL).

Born in Florida, Mackey moved to Wilmington, Delaware where he was a standout defensive end at Christiana High School.

Mackey began his collegiate career at Hinds Community College in Raymond, Mississippi before transferring to Texas Tech in 2011, where he played for two years.

In his final season at Texas Tech in 2012, Mackey earned All-Big 12 honorable mention.

On July 8, the Rattlers defeated the Sioux Falls Storm in the United Bowl by a score of 50–41.