In late January 2019, during his freshman season, Allen registered two double-doubles in a span of six days, leading Utah to wins over Colorado and California.[9] On February 2, he scored a season-high 24 points in an 81–72 loss to Oregon State.[10] As a freshman, Allen averaged 12.2 points, 5.1 rebounds and 2.5 assists per game, earning Pac-12 All-Freshman Team honors.[6] By the time he was a sophomore, he lost 25 lbs (11 kg) and was placed in a leading role, with many key players graduating or transferring.[11] On December 4, 2019, Allen scored a career-high 27 points along with five rebounds and five assists in a 102–95 overtime victory over BYU.[12] On December 18, he scored 25 points to lead Utah to a 69–66 upset win over sixth-ranked Kentucky.[13] Allen averaged 17.3 points, 7.3 rebounds, three assists and 1.2 steals per game as a sophomore and was named to the Second Team All-Pac-12. He was the only Power Five player that season to average at least 17 points, seven rebounds, 2.5 assists and one steal per game.[14] Following the season, he declared for the 2020 NBA draft,[15] before returning to college.[16] As a junior, Allen averaged 17.2 points, 6.4 rebounds and 3.9 assists per game, earning First Team All-Pac-12 honors.[17]
After a coaching change at Utah, Allen transferred to Texas.[18] He was named to the Second-team All-Big 12 as well as the All-Newcomer Team.[19] Allen averaged 12.1 points, 6.4 rebounds, and 1.2 steals per game. On February 11, 2023, Allen scored his 2,000th point in a win against West Virginia.[20]
Professional career
Memphis Hustle / Grizzlies (2023–2024)
After going undrafted in the 2023 NBA draft, Allen joined the Memphis Grizzlies for the 2023 NBA Summer League and on October 16, 2023, he signed with them.[21] However, he was waived two days later[22] and on October 30, he joined the Memphis Hustle[23] where he appeared in 46 matches, while averaging 9.5 points, 4.1 rebounds, 2.7 assists and 1.0 steals in 26.4 minutes.[24]