As a senior in 2016, he was named First-team All-American Athletic Conference after recording 65 tackles and 10.5 sacks as a defensive end.

[7] He was moved to inside linebacker during the Senior Bowl and impressed team representatives and scouts after excelling in practice.

On January 28, 2017, Reddick recorded a game-high nine combined tackles, tying Michigan's Ben Gedeon, as he played for Chicago Bears head coach John Fox's North team that lost 16–15 to the South.

[18] Throughout training camp, Reddick competed for the job as the starting inside linebacker against Deone Bucannon, Karlos Dansby and Zaviar Gooden.

He played the hybrid inside linebacker position after Bucannon suffered an ankle injury and missed a bulk of training camp.

[19] He made his professional regular season debut and first career start in the Cardinals' season-opener at the Detroit Lions and recorded a season-high eight combined tackles in their 35–23 loss.

On November 5, 2017, Reddick was ejected for being involved in a skirmish with Carlos Hyde and finished the game with one solo tackle and a half a sack during their 20–10 victory over the San Francisco 49ers.

In Week 6 against the Dallas Cowboys on Monday Night Football, Reddick recorded two sacks on Andy Dalton during the 38–10 win.

The play injured Purdy's throwing arm, resulting in a torn Ulnar collateral ligament and forcing him to leave the game.

[38] Jets general manager Joe Douglas stated that they would not trade Reddick and that "he is expected to be here with his teammates, and that he will continue to be fined per the CBA if he does not report".

[40] On October 20, after missing the first six games of the season, Reddick and the Jets agreed to a reworked contract, ending his holdout.