He was ruled ineligible to play in his freshman season by the NCAA. A review by the NCAA Eligibility Center determined that some of the coursework he had completed during high school didn't meet NCAA eligibility requirements. There were problems with online courses he had taken while at Huntington Prep as well as concerns about his time at Christian Faith Center. He received a redshirt for the season.
Redshirt Freshman
He started off slow to start the season. He didn't play in the Seminoles first game of the season. He made his debut in the next game against Northeastern and was held scoreless. In the third game of the season, he scored 5 points against the Providence Friars. However, after this his statistics improved quickly as in the next two games he scored 22 and 26 points against UMass and The Citadel respectively. Other notable games he had were against North Carolina, when he scored 35 points; against Miami Hurricanes, when he also scored 35 points, including 30 points in the last 4:38 of the game; and 30 points against Clemson. He averaged 14.9 points per game, becoming only the second freshman to lead Florida State in scoring. He was named to the All-ACC Freshman Team
After going undrafted in the 2017 NBA Draft he joined the New York Knicks for the 2017 NBA Summer League. He signed with the Knicks on a non guaranteed contract, he was waived by the Knicks as one of the final cuts after appearing in preseason games.
On March 5, 2018, the Memphis Grizzlies signed Rathan-Mayes to a 10-day contract. Rathan-Mayes made his NBA debut on the same day, contributed eight points, five assists, two rebounds and two steals in 25 minutes for the Grizzlies in a 98–100 loss to the San Antonio Spurs. Rathan-Mayes' contract expired on March 14, 2018.
Second stint with Westchester Knicks (2018)
On March 14, 2018, the Westchester Knicks announced that they had re-acquired Rathan-Mayes.
On January 8, 2019, the Texas Legends acquired Rathan-Mayes from Westchester Knicks for Jameel Warney. In 25 games played for the Legends, he averaged 14.2 points, 4.6 rebounds, 6 assists and 1.1 steals per game.
On March 28, 2019, Rathan-Mayes joined Bnei Herzliya of the Israeli Premier League, signing for the rest of the season. On April 22, 2019, Rathan-Mayes recorded a season-high 28 points, shooting 6-of-11 from three-point range, along with five rebounds and three assists in a 76–72 win over Ironi Nahariya. He was subsequently named Israeli League Round 28 MVP. At the end of the season Xavier and Bnei Herzliya relegated to the 2nd tier.
On October 26, 2019, Rathan-Mayes was included in the training camp roster of the Texas Legends. Rathan-Mayes was later included in the opening night roster of the Texas Legends.
Agua Caliente Clippers (2019–present)
On December 3, 2019, the Agua Caliente Clippers announced that they had acquired Rathan-Mayes from the Texas Legends for the returning rights to Demarcus Holland and a 3rd round draft pick in the 2020 NBA G League Draft.
Rathan-Mayes represented his country, Canada, twice in international competition. He participated at the 2012 U-18 Americas Championship and the 2013 U-19 World Championship.
