Mattison became the latest running back to excel in Boise, earning first-team All-Mountain West Conference accolades in 2018. He finished in the top 10 nationally in rushes (302), rushing yards (1,415), and rushing touchdowns (17) as a junior for the Broncos. In the MWC Championship Game loss to Fresno State, he carried the ball 40 times for 200 yards and a score. League coaches awarded him honorable mention notice in 2017, as he covered 1,086 yards and scored a dozen times on 212 carries (5.1 average) in 14 games (nine starts). Mattison contributed as a true freshman, as well, playing in all 13 games (67-328-4.9, four TDs). He was a part of Boise's passing game during his three-year career, catching 60 passes for 511 yards (8.

Mattison became the latest running back to excel in Boise, earning first-team All-Mountain West Conference accolades in 2018. He finished in the top 10 nationally in rushes (302), rushing yards (1,415), and rushing touchdowns (17) as a junior for the Broncos. In the MWC Championship Game loss to Fresno State, he carried the ball 40 times for 200 yards and a score. League coaches awarded him honorable mention notice in 2017, as he covered 1,086 yards and scored a dozen times on 212 carries (5.1 average) in 14 games (nine starts). Mattison contributed as a true freshman, as well, playing in all 13 games (67-328-4.9, four TDs). He was a part of Boise's passing game during his three-year career, catching 60 passes for 511 yards (8.5) and one score. At San Bernardino High School, Mattison ran for over 2,000 yards as a junior and senior while also winning league titles in wrestling and the 110-meter hurdles.

Productive, willful runner whose combination of functional patience and aggressive urgency helped him find his niche as an every-down workhorse. While he has the ability to create yards for himself with adequate elusiveness and power, he's not a slasher or banger by NFL standards and he lacks burst to produce chunk plays on a regular basis. Mattison is a jack-of-all-trades backup with the ability to step into a heavy-duty role if called upon. His talent as a pass-catcher could move him up the RB food-chain.