He played college football at Oregon and was selected in the seventh round of the 2016 NFL draft by the Philadelphia Eagles.

He had many dynamic plays on the Ducks' fast-paced defense, including two fumbles recovered for touchdowns, one of which was the notorious drop at the 1-yard line by Utah wide receiver Kaelin Clay in the Utah-Oregon game on November 8, 2014, which Walker returned 99 yards for an Oregon touchdown.

[1][2] Walker was not one of the 39 collegiate linebackers invited to the 2016 NFL Scouting Combine, but competed in Oregon's Pro Day.

[3] Walker was a projected to be a seventh-round pick or priority undrafted free agent by NFL draft experts and scouts.

On August 18, 2016, Walker tore his ACL in a preseason game against the Pittsburgh Steelers, effectively ending his rookie season.

[10] 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.