In his collegiate debut as a true freshman in 2006, Smith intercepted a pass that was deflected by another player against Nebraska. Smith overall, started eight games and came off the bench in five for the Bulldogs and had 38 tackles. His career high in tackles came against North Texas when he had seven, he also had five against Fresno State. Against Fresno State as a sophomore in 2007, Smith equaled his total from the season before with five tackles, but also added a sack on their quarterbackTom Brandstater. For the season, he started 11 games and missed one due to injury and had 42 tackles and three sacks. Smith tied his career high in tackles with seven against Central Arkansas. Against San Jose State in 2008, Smith had seven tackles and one sack. Heading into the Independence Bowl against Northern Illinois, he led the team with five sacks and was third with 65 tackles. He was named as a member of the First-team All-WAC following the regular season. For the season, he had nine tackles on two occasions and was named All-Louisiana. He started every one of the Bulldogs's 13 games. In 2009, Smith was listed at No. 11 on Rivals.com′s preseason defensive tacklepower ranking. He was also named to the 2009 Outland Trophy watch list.
Professional career
Jacksonville Jaguars
Smith was drafted by the Jacksonville Jaguars in the third round of the 2010 NFL Draft. He spent his first two NFL seasons on injured reserve. He registered his first career tackle in the Jaguars' 2012 season opener against the Minnesota Vikings. He was placed on injured reserve on November 28, 2012.
The Jaguars announced that Smith was one of their final preseason cuts on August 30, 2013. However, before the team had officially submitted their cuts, Smith was traded to the Seattle Seahawks on August 31 for a conditional draft pick. He was released by the Seahawks on September 24, 2013.
Detroit Lions
The Lions claimed Smith off waivers on September 25, 2013, and released him on October 2.
Seattle Seahawks (second stint)
Smith was re-signed by the Seattle Seahawks to their practice squad on October 5, 2013. Smith re-signed with Seattle on March 19, 2015. On August 31, 2015, Smith was cut by the Seahawks during the preseason.
On October 13, 2015, the Chicago Bears signed Smith to their practice squad. He was promoted to the active roster on December 22. On May 2, 2016, the Bears released Smith.