Filson played his first professional season with their Rookie league Paintsville Yankees and Class-A (Short Season) Oneonta Yankees in 1979, and split his last between Kansas City and their Triple-A Omaha Royals in 1990. Filson can be seen delivering a single pitch as a Royal in the Ken BurnsdocumentaryBaseball, at the beginning of the section entitled "Extra Innings."
With the Twins, Filson was affectionately nicknamed "Freeze".[4]
Coaching career
In 2003 Filson was hired as pitching coach for the Newark Bears of the independent Atlantic League, Filson remained with the team until 2006.
Filson is currently a pitching instructor at AFC Baseball in Bala Cynwyd, Pennsylvania, where he provides instruction to players at Harriton High School, Radnor High School, the Chester County Crawdads, and Wayne Wolverines.