He played college football for the Boise State Broncos and was selected by the Minnesota Vikings in the third round of the 2019 NFL draft.

[2] Mattison was selected to play in the Inland Valley Football Classic following his senior season.

As a true freshman at Boise State in 2016, Mattison appeared in all 13 games and had 328 yards on 67 carries with four touchdowns.

He was the Offensive MVP of the 2018 Mountain West Conference Football Championship Game after rushing for 200 yards and a touchdown.

[7] He cited his reason as "You can only play as long as your body lets you, and at this position, you can't assume it'll last forever."

Mattison didn't miss a game in his college career, despite needing offseason surgeries on his shoulder and ankle.

[10] He made his NFL debut in the 2019 regular season opener against the Atlanta Falcons; Mattison had nine carries for 49 yards in the 28–12 victory.

[13] In a Week 5 Sunday Night Football game against the Seattle Seahawks, Mattison finished with 20 carries for 112 rushing yards as the Vikings narrowly lost 26–27.