Duval attended Saint Benedict's Preparatory School in Newark, New Jersey during his Freshman and Sophomore years. As a sophomore in 2014-15 Duval led the Gray Bees to a 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 Peach Jam Championship. In September 2015, Duval transferred to Advanced Preparatory International in Dallas, Texas for his Junior season. As a junior in 2015–16, Duval averaged 16.8 points per game and 7.0 assists per game. In the spring and summer of 2016, Duval competed in the Under Armour Association circuit for the AAU team, WE-R1. He led WE-R1 to an Under Armour Association Championship, becoming the first player to win both under armour and Nike peach jam championships. Duval averaged 16.3 points per game and 3.8 assists per game in the 2016 Under Armour Association circuit. Duval was then invited to the Under Armour Elite 24 in Brooklyn, New York, where Duval finished the game with 25 points and 7 assists leading team drive to 140-136 victory in overtime. In late 2016, Duval transferred to IMG Academy in Bradenton, Florida. As a senior, Duval averaged 16.1 points per game and 7.5 assists per game leading IMG to a record. He played in the McDonald's All-American Game and Jordan Brand Classic. Duval was considered one of the best players in the 2017 recruiting class by Scout.com, Rivals.com and ESPN. In 2015 he was ranked by Scout as the third ranked prospect in all of high school in their "Ultimate 100" list.
College career
On May 15, 2017, Duval committed to attend and play for Duke University, joining fellow recruits Wendell Carter Jr., Gary Trent Jr. and Marvin Bagley III later on that year. During this time, he was projected to be a first round pick in the 2018 NBA Draft. On November 11, Duval scored 15 points and had 12 assists in a 99–69 win over Utah Valley. 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. On November 23, he scored 22 points while shooting 7-of-14 from the field helping the Blue Devils defeat Portland State 99–81. On November 29, Duval scored 15 points and 6 assist in a 91–81 win over Indiana in the ACC-Big Ten Challenge. On December 30, he scored 16 points and 4 assists in a 100-93 victory against Florida State. On January 15, Duval 17 points and 8 assists in an 83–75 victory over Miami. On March 15, Duval notched 19 points and 8 assists in an 89–67 win over Iona. On March 25, he scored 20 points and 6 assists in an 85–81 overtime loss against Kansas in the Elite 8. In his freshman season at Duke, Duval saw at action in a total of 37 games as a freshman and averaged 10.9 points, 5.6 assists, and 2.0 rebounds per game. 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.
On June 21, 2018, Duval did not get drafted by any team in the 2018 NBA draft. He was the first one-and-done player in Duke history to go undrafted. Afterwards, he signed with the Houston Rockets for the NBA Summer League. On July 24, Duval signed a two-way contract with the Milwaukee Bucks, his contract split time between the Bucks and their NBA G League affiliate, the Wisconsin Herd. Duval made his NBA debut on February 8, 2019, scoring two points and recording one assist in a win over the Dallas Mavericks. On March 24, 2019, the Milwaukee Bucks waived Duval.
Houston Rockets (2019)
On March 26, 2019, Duval was claimed by the Houston Rockets on a two-way contract. He did not appear in a game for them during the regular season and his late signing ruled him ineligible for the playoffs. He instead spent the majority of his time signed to the Rockets in the G League with the Rio Grande Valley Vipers. Duval played at the 2019 NBA Summer League in Las Vegas with the Houston Rockets.
Iowa Wolves (2019-present)
On October 26, 2019, Duval was selected by the Iowa Wolves with the fifth overall pick in the first round of the 2019 NBA G League Draft. 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.
National team career
Duval participated in the 2016, 2015 and 2014 USA Men's Junior National Team October minicamps.
