Spears rushed for 192 yards and one touchdown and caught five passes for 133 yards and one touchdown in four games during his freshman season at Tulane.[4][5] He began his sophomore season as the Green Wave's starting running back and rushed 37 times for 274 yards and two touchdowns before suffering a season-ending injury in Week 3 and using a medical redshirt.[6] As a redshirt sophomore, Spears gained 863 yards and scored nine touchdowns on 129 carries.[7] He was named the American Athletic Conference Offensive Player of the Year as a redshirt junior.[8] He was ranked the 6th best college football player nationwide among the "100 Best Players of the College Football Bowl Season 2022–2023" by College Football News.[9]
Spears was drafted by the Tennessee Titans in the third round, 81st overall, of the 2023 NFL draft.[12] He shared a backfield that had Derrick Henry as the primary running back.[13] In Week 5, against the Indianapolis Colts, he scored his first professional touchdown on a 19-yard rush.[14] He finished his rookie season with 453 rushing yards and two touchdowns along with 52 catches for 385 yards and one touchdown.[15]
Spears returned for the 2024 season, now sharing the backfield with newly signed Tony Pollard after Henry's departure. He was the only Titans player that season to record two touchdowns in two consecutive games during Week 15 and Week 16. He appeared in 12 games, missing parts of the season due to injury. He finished the season with 84 carries for 312 rushing yards and four rushing touchdowns, along with 30 receptions for 224 yards and a receiving touchdown.[16]