[4] In his senior season in 2015–16, he tallied 108 goals and 53 assists, helping the team to a 20–3 record, and was named the USA Today boys' lacrosse player of the year.
[2][7] Denver made it to the semifinals of the 2017 NCAA tournament but lost to eventual champions Maryland, though Walker was named to the all-tournament team.
[2][9] Walker led the Pioneers with 70 points on 48 goals and 22 assists in the 2018 season, being nominated for the Tewaaraton Award and named third-team USILA All-American.
[2][11] A four-time first-team Big East honoree, Walker holds multiple career program records, including most points (279) and most assists (98).
[17] Walker represented Canada at the Under-19 World Lacrosse Championships in 2016, where they finished runners-up to the United States.
In September 2022, Walker moved to Kansas City, Missouri, to become the director of Building Champions Lacrosse, an academy program at the HomeField KC sports facility.