As a sophomore in 2014–15, Duval led the Gray Bees to a 31–6 record and NCSAA state championship in which he scored 25 points and had 8 assists.

Prior to his sophomore year, Duval along with Isaiah Briscoe for the AAU team, New Jersey Playaz won the 2014 Nike Elite Youth Basketball League (EYBL) Peach Jam Championship.

A consensus five-star recruit, he was selected to play in the McDonald's All-American Game and Jordan Brand Classic.

[8] On May 15, 2017, Duval committed to attend and play for Duke University, joining fellow recruits Wendell Carter Jr., Gary Trent Jr., Jordan Tucker, and Marvin Bagley III later on that year.

[12] On November 14, Duval achieved his second double-double in the season, scoring 17 points, 10 assists, and six steals in an 88–81 victory against Michigan State in the Champions Classic.

[13] On November 23, he scored 22 points while shooting 7-of-14 from the field helping the Blue Devils defeat Portland State 99–81.

[21] Following Duke's loss in the 2018 NCAA men's basketball tournament, Duval announced his intention to forgo his final three seasons of collegiate eligibility and declare for the 2018 NBA draft.

[25] Duval made his NBA debut on February 8, 2019, scoring two points and recording one assist in a win over the Dallas Mavericks.

[32] On February 24, 2020, he posted 14 points, five rebounds, five assists, two blocks and one steal in a 152–148 loss to the South Bay Lakers.