He played college football for the Alabama Crimson Tide, where he was recognized as a unanimous All-American and was a member of two BCS National Championship teams.

He played football at Escambia High School[7] Richardson finished his senior season with 2,100 yards on 228 carries scoring 25 touchdowns.

In a game against Milton High School in September 2008, Richardson rushed for 419 yards on 29 carries and scored six touchdowns, a performance that earned him a selection as the first ESPN RISE National Football Player of the Week.

[8] As a junior, Richardson also reached the 400-yard plateau, as he ran for 407 yards in his opening game against Tate High School.

He finished his junior season (8 games) with 1,390 yards and 13 touchdowns, and received FSWA All-State 5A second team honors.

He made the FSWA 5A All-State First Team as a senior, and was named 5A Florida Player of the Year and a finalist for the 2008 Mr. Football.

Richardson also received consensus All-American honors and was named to the Orlando Sentinel's All Southern Team (Florida).

In 2008, he captured a regional title in the 100-meter dash (10.81 s) and placed 5th at the state meet with a time of 10.9 seconds (World-class sprinter Jeff Demps won the event).

[11] Richardson was frequently compared to Emmitt Smith, who also starred at Escambia (1987 graduate), but his physique and running style are more similar to Earl Campbell.

[15] In his first year at Alabama, Richardson stepped in quickly for the departed Glen Coffee, and shared time at the tailback position with Roy Upchurch and Mark Ingram, Jr.[16] When recruited, Crimson Tide coach Nick Saban called Richardson, "the real key to the class," and "an outstanding player at a position that a young player can contribute next year.

[20] Richardson was also named to the 2009 SEC All-Freshman team alongside Barrett Jones and Nico Johnson.

[21] He also contributed significantly in the 2010 BCS National Championship against the Texas Longhorns with 109 yards rushing and 2 touchdowns.

[31] With the departure of Mark Ingram II to the NFL, Richardson took over the starting role at running back.

[34][35] He finished third in the Heisman Trophy voting behind eventual winner Robert Griffin III and Andrew Luck.

[43] On January 12, 2012, Richardson declared for the 2012 NFL draft, thus forgoing his final year of collegiate eligibility.

[44] At the time of his announcement, he was projected as a first round pick and the top running back prospect in the draft.

[44] Entering his junior season, Richardson was widely regarded as the best running back available in the 2012 NFL draft, and he cemented his reputation with strong play over the course of the year.

[45][46][47] After undergoing a minor knee surgery in February 2012, Richardson did not participate in drills at the 2012 NFL Combine.

[50] By March 2012, Richardson was widely projected to be a top six draft choice by the majority of analysts and scouts, with the Cleveland Browns, Tampa Bay Buccaneers, and St. Louis Rams rumored to be showing the most interest.

[61][62] On August 9, 2012, Richardson underwent arthroscopic surgery to remove some cartilage fragments in his left knee.

In his debut against the Philadelphia Eagles, he rushed for 39 yards on 19 carries, being limited in his touches after having just come off the disabled list.

Richardson fumbled on his first career playoff carry against the Kansas City Chiefs in the Colts' Wild Card 45–44 victory.

[98] Richardson finished his time in the AAF's short existence as arguably the most productive player[99] with the most rushes per game, and had a league best 12 total touchdowns.