[1] He was a three-year starter for the Knights and contributed on offense as a running back, on defense as a cornerback, and a returner on special teams.

[3] Kelly committed to the University of Tennessee to play college football under head coach Butch Jones.

[6] After various appearances throughout the season, he scored his first career touchdown, a one-yard rush in the fourth quarter, in the 2016 Outback Bowl in the 45–6 victory over the Northwestern Wildcats.

He made his season debut in the 2016 Pilot Flying J Battle at Bristol against Virginia Tech.

[9] Later on, an opportunity arose for Kelly, as Hurd had some team issues and did not play in the game against Texas A&M.

[13] After some solid performances to close the regular season, he had 15 carries for 70 yards and a touchdown in the victory over Nebraska in the 2016 Music City Bowl.

[15] With Kamara entering the 2017 NFL draft, Kelly returned as the main running back for the Volunteers for the 2017 season.

In the season opener against Georgia Tech at Mercedes-Benz Stadium, Kelly had a career day in Tennessee's 42–41 double overtime victory.

[27] He was selected by the Rams through a pick that was previously acquired from the New York Giants in exchange for Alec Ogletree.

[28] He joined a running backs unit that contained Todd Gurley and Malcolm Brown.

[29] During the game against the Detroit Lions in Week 13, Brown suffered a clavicle injury, giving Kelly the opportunity for playing time.

[30] He made his NFL debut on Special Teams against the Chicago Bears in Week 14, playing seven snaps.

[33] Gurley again was inactive for Week 17 against the San Francisco 49ers, giving Kelly the opportunity to have 15 carries for 30 rushing yards and a 18-yard reception.

[34] In the Divisional Round against the Dallas Cowboys, he had a special teams tackle in his playoff debut.

[35] He saw playing time on special teams in the NFC Championship Game and Super Bowl LIII.

[38] Kelly was waived during final roster cuts on August 31, 2019,[39] but was signed the next day to the Rams' practice squad.