He played college football for the Western Kentucky Hilltoppers, earning second-team All-American honors in 2011.

Rainey signed with the Baltimore Ravens as an undrafted free agent after the 2012 NFL draft.

In 2011, Rainey had 1,695 rushing yards and 17 total touchdowns while playing running back at Western Kentucky University.

He was named the Sun Belt Conference Offensive Player of the Year in 2010 as well as earning All-American honors from SI.com.

[5] In 2009, he totaled over 2,100 yards and gained notoriety as one of the premier Kick Returners in College Football.

That list includes LaDainian Tomlinson (TCU), Ray Rice (Rutgers), Steven Jackson (Oregon State), DeAngelo Williams (Memphis), and Darren McFadden (Arkansas).

On October 16, 2012, he was promoted to the active roster after the team placed Lardarius Webb on injured reserve.

Due to injuries to Doug Martin and Mike James he would finish his debut Buccaneer season as the team's leading rusher with 137 attempts for 523 yards and 5 touchdowns.