Long missed the first month of the season due to a summer knee injury. As a redshirt sophomore for the 2017 Mountaineers, his best statistics were his 18-tackle (including a school record 7 for a loss (meaning the offense lost yardage as a result of his tackle)) effort against the Oklahoma State Cowboys on October 28 and his 2.5-quarterback sack performance in the December 26, 2017 Heart of Dallas Bowl against the Utah Utes.
Among his best games as a redshirt junior for the 2018 team were his 15-tackle (3 for a loss) effort against Texas Tech on September 29 and his 3-sack performance on November 10 against TCU. That season, he was named as a 2018 first team All-Big 12 selection and as the Big 12 Defensive Player of the Year, after leading the Big 12 in tackles for a loss. Long is the second Mountaineer to be named a conference defensive MVP (Canute Curtis, 1996 Big East), and first since the Mountaineers joined the Big 12. Long earned 2018 College Football All-America Team second team recognition by the Walter Camp Football Foundation, and the Associated Press. On December 30, 2018, Long announced that he would forgo his final year of eligibility and declare for the 2019 NFL Draft.