As a dual-threat quarterback, he was rated a two-star recruit by Rivals.com[2] and committed to play college football at San Diego State.

As a true freshman, Kelly converted to safety and was a backup, before suffering a knee injury that was complicated by compartment syndrome, which forced him to miss the final 6 games of the season.

He registered a career-high 68 tackles (5 for loss), two sacks, and two forced fumbles, 3 interceptions and 8 passes defensed.

[1] Kelly was signed as an undrafted free agent by the Dallas Cowboys after the 2018 NFL draft on April 30.

[5] On October 27, 2018, Kelly was signed by the San Diego Fleet of the Alliance of American Football for the 2019 AAF season.

[8] In practice before the week 3 game, head coach Mike Martz announced that Kelly would be moved back to cornerback due to injuries.

[13] In week 5 against the Baltimore Ravens, Kelly recorded his first career interception off Lamar Jackson in the 26–23 loss.

[15] The charges were dropped by December 2020, and Kelly was fined half of a game salary by the NFL.

[17] He played in all 14 regular season games in 2021 where he had 36 defensive tackles, 10 pass deflections, one sack, and one interception.