In his first year at Kentucky, Smith started all 12 games and recorded 59 tackles and six sacks, which ranked seventh in the Southeastern Conference (SEC).

[7] On January 17, 2015, Smith appeared in the 2015 East–West Shrine Game and recorded two combined tackles and one sack to help the East defeat the West 19–3.

On January 24, 2015, Smith appeared in the Reese's Senior Bowl and helped the North team defeat the South 34–13.

At the conclusion of the pre-draft process, Smith was projected to be a third or fourth round pick by NFL draft experts and scouts.

Head coach John Harbaugh named Smith the backup weakside linebacker, behind Terrell Suggs, to start the regular season.

[22] In Smith's debut as a Packer in week 1, he made 3 tackles and sacked Mitchell Trubisky once in the 10–3 win over the Chicago Bears.

[25] In week 12 against the San Francisco 49ers, Smith recorded a team high 6 tackles and sacked Jimmy Garoppolo once in the 37–8 loss.

In the Divisional Round of the playoffs against the Seattle Seahawks, Smith recorded 2 sacks on Russell Wilson during the 28–23 win.

[29] In Week 3 of the 2020 season against the New Orleans Saints, Smith forced a fumble on Taysom Hill that was recovered by the Packers during the 37–30 win.

[36] Smith played just 18 snaps during the 3–38 loss, behind second-year teammate Jonathan Garvin, and was called for a roughing the passer penalty that negated a Darnell Savage interception.

[42] On January 22, Smith, along with fellow linebacker Whitney Mercilus, were officially activated off injured reserve ahead of the Packers' first playoff game in the Divisional Round against the San Francisco 49ers.

[43] In his first snap since Week 1, rushing on the interior on a 3rd and 14, Smith beat left guard Laken Tomlinson to sack quarterback Jimmy Garoppolo.

[52] Smith made his Lions debut on November 17, 2024, against the Jacksonville Jaguars,[53] where he recorded half of a sack on quarterback Mac Jones in a 52–6 win.

On September 29, 2019, Smith was cited by the Racine County Sheriff's Office for possession of marijuana and speeding in a construction zone.

Smith and teammates Rashan Gary and Kingsley Keke were returning to Green Bay from Chicago when a deputy stopped them for driving 81 mph in a 60-mph construction zone near the intersection of Interstate 94 and Highway 20 in the town of Mount Pleasant.