Walker attended Reading Senior High School in Reading, Pennsylvania. Walker made his varsity basketball debut as a freshman and played 27 games averaging 8 points per game, and later as a sophomore he averaged 16.9 points per game in a short season due to injury. And in 29 games, as a junior, he averaged 17.1 points per game. During his senior year he averaged a career best 18.4 points per game and surpassed Reading High grad and former NBA player Donyell Marshall's school record in points by finishing with 1,828. On March 25, 2017, Walker led the Red Knights to their first state championship in the program's 117-year history in a 64-60 win over the Pine-Richland Rams. Walker finished the game with 22 points, 8 rebounds, 4 steals, and 3 assists. During the season Walker signed with the Miami Hurricanes, passing on offers from Villanova, Kentucky, Syracuse and Arizona.
College career
Walker made his collegiate debut on November 10, 2017, recording 10 points and a season-high 5 assists coming off the bench in a 77–45 blowout win over Gardner-Webb University. He created new highs of 12 points and 5 rebounds on December 2 in an 80–52 blowout win against Princeton University before recording season-highs of 26 points and 7 rebounds during his first collegiate start three days later in a 69–54 win over Boston University. Against Louisville, he scored a game-high 25 points including an acrobatic layup in traffic to force overtime. In a game against Boston College, he hit a 3-pointer with two seconds remaining to win 79-78. Walker finished the season averaging 11.5 points per game, leading the Hurricanes. After his sole season with Miami concluded, Walker declared for the 2018 NBA draft.
On June 21, 2018, Walker was selected with the 18th overall pick by the San Antonio Spurs in the 2018 NBA draft. Walker was later included in the 2018 NBA Summer League roster of the Spurs. On July 11, 2018, the Spurs announced that they signed Walker. On October 6, 2018, Walker was revealed to have a right medial meniscus tear. On November 25, 2018, the San Antonio Spurs assigned Walker the first time of the season to the Austin Spurs. Walker made his NBA debut on January 3, 2019 in a 125–107 win against the Toronto Raptors, scoring three points and grabbing one rebound in five minutes of play.
2019–20 season
On December 4, 2019, Walker scored a career-high twenty eight points, including nineteen in the fourth quarter, in a 135–133 double overtime win over the Houston Rockets with four rebounds, three steals and a block.
Career statistics
NBA
Regular season
Playoffs
College
Personal life
During the 2018 NBA Draft Combine, Walker made public his interest in conspiracy theories. In 2018, Walker also donated 300 pairs of Adidas sneakers to his hometown youth blacktop league. Walker has a dog named Zola, who appeared with him in a PETAad campaign, reminding people not to leave their dogs in hot, parked cars. In June of 2020, Walker revealed he had been the victim of frequent sexual abuse by family members as an adolescent, and had grown out his trademark long hairstyle as a coping mechanism. In deciding to cut his hair, Walker described the act as having "shed my skin mentally, emotionally, physically and spiritually."
