As a senior, Vassell averaged 21.6 points and 8.9 rebounds per game and was named the regional Player of the Year by the Gwinnett Daily Post.

[5] Vassell made a three-pointer with 4.5 seconds left in regulation to force overtime in the Seminoles' 65–63 win over Virginia Tech in the quarterfinals of the 2019 ACC men's basketball tournament.

[22] On April 17, 2021, Vassell scored a season-high 18 points, alongside three rebounds, two assists and two blocks, in a 111–85 win over the Phoenix Suns.

[23] On February 26, 2022, Vassell scored a regular season-high 22 points, alongside five rebounds and four assists, in a 129–133 loss to the Miami Heat.

[25] Despite a season-high 23 points, alongside two rebounds and three assists, from Vassell, the Spurs were defeated by the New Orleans Pelicans in the play-in tournament with a 103–113 loss.

[28] Vassell underwent an arthroscopic procedure on his left knee on January 11, 2023[29] and made his return on March 2, 2023, in a victory against the Indiana Pacers.

[34] On December 15, 2023, Vassell scored a career-high 36 points, alongside six rebounds and three assists, in a 129–115 win against the Los Angeles Lakers.