Pre-draft

Walker was not one of the 39 collegiate linebackers invited to the 2016 NFL Scouting Combine, but completed in Oregon's Pro Day.^[2] Walker was a projected to be a seventh-round pick or priority undrafted free agent by NFL draft experts and scouts. He was ranked the 19th best inside linebacker prospect in the draft by NFLDraftScout.com.^[3]

Philadelphia Eagles

The Philadelphia Eagles selected Walker in the seventh round (251st overall) of the 2016 NFL Draft. He was the 36th and last linebacker selected in 2016.^[4] The pick used to select him was a conditional pick that was traded from the Arizona Cardinals in exchange for Matt Barkley.^[5]

On May 4, 2016, Walker signed his four-year, rookie million contract.^[6] Throughout training camp, he competed against Najee Goode for a roster spot. On August 18, 2016, Walker tore his ACL in a preseason game against the Pittsburgh Steelers, effectively ending his rookie season.^[7] On August 28, 2016, Walker was placed on injured reserve.^[8]

He made his professional debut in the Philadelphia Eagles season-opening 30–17 win at the Washington Redskins. On September 24, 2017, Walker assisted on one tackle during the Eagles' 27–24 victory against the New York Giants. His first career tackle was with Jalen Mills as they teamed up to tackle Giants' wide receiver Sterling Shepard after he made a 10-yard reception in the first quarter.^[9] On October 29, 2017, Walker earned his first career start and made a season-high three combined tackles in a 33–10 win over the San Francisco 49ers. He was named the starting middle linebacker after Jordan Hicks suffered a torn Achilles and was placed on injured reserve for the remainder of the season. During a Week 12 matchup against the Chicago Bears, Walker suffered a neck injury and was placed on injured reserve on December 29, 2017.^[10] He finished the season with ten combined tackles (six solo) and a pass deflection in 12 games and three starts.^[11] The Eagles won Super Bowl LII against the New England Patriots by a score of 41-33.^[12]

On September 2, 2018, Walker was waived by the Eagles and was signed to the practice squad the next day.^[13]

Arizona Cardinals (first stint)

On September 19, 2018, Walker was signed by the Arizona Cardinals off the Eagles practice squad.^[14]

San Francisco 49ers

On March 24, 2020, Walker signed a one-year contract with the San Francisco 49ers.^[15][16] He was released on September 5, 2020, and signed to the practice squad the next day.^[17][18] He was elevated to the active roster on September 26 for the team's week 3 game against the New York Giants, and reverted to the practice squad after the game on September 28.^[19][20] He was elevated again on October 3 for the week 4 game against the Eagles,^[20] and reverted to the practice squad again after the game on October 5. He was signed to the active roster on October 21.^[21] He was placed on the team's reserve/COVID-19 list by the team on November 19, 2020,^[22] and activated on November 28.^[23]

Washington Football Team

Walker signed with the Washington Football Team on May 19, 2021.^[24] He was released on August 31, 2021.^[25]

Arizona Cardinals (second stint)

On October 13, 2021, Walker was signed to the Cardinals practice squad.^[26] He was promoted to the active roster on December 21.^[27] He was waived on January 11, 2022 and re-signed to the practice squad. He signed a reserve/future contract with the Cardinals on January 19, 2022.^[28]

On August 29, 2022, Walker was released by the Cardinals.^[29]