 After a spell as a wartime guest with Tottenham Hotspur, Hopkin joined Manchester United in 1919.He made his debut away to Derby County on 30 August 1919, playing on the left wing in a 1–1 draw at the Baseball Ground.He missed just three games in his first season with the club and scored eight goals in 41 appearances, his first coming in a 3–3 away draw in the Manchester derby against Manchester City on 11 October 1919.