College: Mathis played his final collegiate season at Nebraska where he appeared in every game with two starts. He finished second on the team with 3.5 sacks and added five tackles for loss to go along with 50 total tackles and two pass breakups. Before transferring to Nebraska, Mathis played in 38 games (34 starts) in four seasons at TCU. He was a Second-Team All-Big 12 selection in 2020 and 2021 and tallied 135 tackles, 30.5 tackles for loss, 15.5 sacks and four pass breakups in his TCU career. In his final season at TCU in 2021, he started all 12 games and notched 45 tackles, 4.0 sacks and seven tackles for loss. He tied for the team lead in sacks, ranked second in tackles for loss, third in pass breakups (three) and fifth in tackles (45). Mathis had a breakout 2020 campaign, starting all 10 games in the pandemic-shortened season. He led the Big 12 and ranked 12th nationally in sacks per game, averaging nearly 1.0 sack per contest. He finished the year with 9.0 sacks, which was the most by a Horned Frog in three seasons. He totaled 46 tackles on the season, with 14 tackles for loss, a forced fumble and a fumble recovery. In 2019, he started all 12 games and finished fifth on the team with 40 tackles, second on the team with nine tackles for loss, and tallied 2.5 sacks. He appeared in four games and registered three tackles and a half tackle for loss in 2018 in a year he redshirted.
Personal: Coming out of high school, Mathis was a three-star prospect and ranked among the top 100 players in the state of Texas. He recorded 75 tackles with 13 tackles for loss and 7.0 sacks as a senior at Manor High School. As a junior, he was a First-Team All-District honoree. He chose to attend TCU over Oklahoma, Texas and Texas Tech. Mathis earned his degree in general studies from TCU and took graduate courses at Nebraska.