Coates, a member of the army like several other players of the time, played for Exeter City in the Plymouth and District League before the club turned professional in 1908.

A so-called “battery man” based at Topsham Barracks, he made his debut against Green Waves (Plymouth) on 30 March 1907 and played in a variety of  positions during his four-match first-team career which concluded at the end of the 1906/07 season.