As a true freshman at East Carolina in 2020, Mitchell appeared in nine games while starting two, and posted 88 rush attempts for 443 yards and two touchdowns, as well as 11 receptions for 75 yards and one touchdown.[6][7] In 2021, he started all 12 games and recorded over 1,000 rushing yards, becoming the first to do so at ECU since Tay Cooper in 2013.[8] He was a first-team all-conference choice and led the American Athletic Conference (AAC) in both total rushing yards (1,132) and all-purpose yards per game (115.83), while additionally placing high in the conference leaderboards in four other statistics.[8] He posted a total of four 100-yard rushing games that season, including a 222-yard performance against Tulane which was the best all-time for an ECU freshman.[8]
As a sophomore in 2022, Mitchell ran for 1,452 yards and scored 14 touchdowns, while being the national FBS leader in runs of more than 10 yards, with 54.[9] He ran for over 100 yards in nine out of their 12 games, additionally tallying 27 catches for 252 yards and one score.[10] He was named an honorable mention All-American by Pro Football Focus (PFF) and was first-team All-AAC for the second straight year.[11] Mitchell declared for the NFL draft after the season, and finished his stint at East Carolina with 3,027 rushing yards and an average of 6.5 yards-per-carry.[6]
Mitchell was projected to be selected in the 2023 NFL draft.[11] He was also selected in the fourth round of the 2023 USFL draft by the New Orleans Breakers.[14] On May 5, 2023, Mitchell was signed by the Ravens as an undrafted free agent.[15]Pro Football Focus considered Mitchell to be one of the ten best undrafted free agent signings from the 2023 NFL Draft class.[16] On August 29, 2023, the Ravens announced that he had made the initial 53-man roster, but he was placed on injured reserve two days later.[17][18][19]
Mitchell was activated off of injured reserve on October 14,[20] and made his NFL debut the next day against the Tennessee Titans in Week 6, playing exclusively on the special teams in the 24–16 win.[21] In Week 9, he ran for 138 yards on nine carries and scored his first NFL rushing touchdown (he also recorded a -4 yard reception) in a 37–3 rout of the Seattle Seahawks. His performance earned him the FedEx Ground Player of Week Award.[22]
During the Week 15 23–7 win over the Jacksonville Jaguars, Mitchell injured his knee in the fourth quarter after being tackled by Jaguars' safety Andrew Wingard. Mitchell was immediately ruled out and carted back to the locker room for further evaluation. After the game, it was announced he fully tore his ACL and would miss the rest of the season. He was placed on injured reserve on December 19.[23] He finished his rookie season with 47 carries for 396 rushing yards and two rushing touchdowns in eight games and two starts.[24]