He played college football for the Alabama Crimson Tide, earning unanimous All-American honors in 2008.

[7] Mike Farrell of The Sporting News called Smith "the best offensive line prospect since Orlando Pace.

[13][14] He was also a first-team All-SEC selection and shared the league's Jacobs Blocking Trophy with Arkansas center Jonathan Luigs.

[12] On December 29, 2008, Smith was suspended from playing in the 2009 Sugar Bowl,[16]—a game Alabama lost 31–17 to the Utah Utes—, reportedly because he dealt with an agent.

[17] A few days later, Smith declared himself eligible for the 2009 NFL draft, and at the time he was considered a lock to be a Top 5 pick.

[18] Widely believed to be the best run-blocking tackle in the 2009 NFL draft, Smith drew comparisons to Jason Peters.

[35] He also looked out of shape as he ran 40 yards shirtless, clocking at a slow 5.28, and had a disappointing 19 repetitions on the bench with 225 pounds.

Smith, however, did not inform his group leader at the combine before he left, and later apologized, stating: "If I had the chance to do it all over, I wouldn't have handled it the way I did.

[51] Just days after ending his holdout, Smith fractured his left foot during a non-contact drill at training camp in his first week of practice after missing most of preseason.

It was also reported that in the preseason, he spoke with the Bengals starting left tackle, Andrew Whitworth, about how "it's my time to step up."

In week 1 at Cleveland, he averted a giveaway by recovering an Andy Dalton fumble at the Bengals eight-yard line.

He helped running back BenJarvus Green-Ellis rank first in the league in third-and-one rushing conversions (93.3 percent success rate, on 14 of 15) and was part of a run-blocking effort for Green-Ellis to gain at least 100 yards four times in a five-game stretch (Games 10-12 and 14), with 168.2 team average in that span.

It was reported by NFL.com's Ian Rapoport that Smith agreed to a three-year, $18 million contract during the second round of the 2013 NFL draft.

[53] He started in games 1-11 and 13–16 at right tackle, and came off bench in week 12, helping the Bengals rank tied for sixth in scoring and tenth in net offense.

In the wild card playoff game on January 5, 2014, he contributed to a 439-yard offensive output against the San Diego Chargers.

He was credited by coaches with the key block on Giovani Bernard’s 89-yard touchdown run, the second-longest in Bengals history, on October 12 against the Carolina Panthers.

On September 13 at Oakland, he helped lead pass protection that allowed no sacks and supported 396 yards of net offense.

The following week, he contributed with a second straight sack-free game against the San Diego Chargers, in which the rushing offense put up 175 yards on the ground.

In week 3, he provided pass protection for Andy Dalton to register a career-high 383 yards on September 27 against the Baltimore Ravens.

On October 11 against the Seattle Seahawks, he helped the offense accumulate 419 total yards and score 17 points in the fourth quarter to overcome a 24–7 deficit.

In week 6 at Buffalo, he helped allow no sacks as Andy Dalton posted 118.6 passer rating, with three scores and no interceptions.

On March 18, 2016, Smith signed a one-year contract with the Minnesota Vikings worth up to $3.5 million with $500,000 guaranteed.

His younger brother, Christian Smith, formerly played wide receiver and cornerback at Hampton University.

[69] He is also a cousin of Dominic Lee, a former defensive lineman for the Alabama Crimson Tide[70] and Desmond Jennings, a professional baseball outfielder.