He played college football for the Michigan Wolverines from 1997 to 2000, breaking their career rushing record at the time with a four-year total of 4,472 yards.

As a senior he rushed for 1,733 yards with 18 touchdowns, and was selected as a first-team All-Big Ten running back.

[4] He was named a first-team All-American and rated as the second-best running back in the country by the Prep Football Report.

[9] On October 21, 2001, Thomas set two Bears rookie records with 188 rushing yards and a 8.55 yards/carry average in a 24–0 victory over the Cincinnati Bengals.

[10] He set his third franchise rookie record in the season finale with 33 carries; he also had 160 yards and a touchdown in the clinching victory over Jacksonville.

With 1,183 rushing yards during the 2001 season, Thomas helped lead the Bears to a 13–3 record and an NFC Central championship.

[14] In May 2005, Thomas signed a one-year contract with the Dallas Cowboys and was expected to be the backup running back to Julius Jones.

[3] Thomas' ineffectiveness in limited duty, his inability to play special teams, and the emergence of Marion Barber III as the primary backup led Dallas to release him in November 2005.

He was quickly signed by New Orleans after they lost Deuce McAllister with a season ending knee injury.