Key was born in the Dennistoun district of Glasgow, and played at Junior level for Parkhead[3][4] before stepping up to Heart of Midlothian in 1899.

With Hearts, Key won the Scottish Cup in 1901[5] and the following season, was capped for Scotland against Ireland,[6] also appearing in the away leg of the 'World Championship' against Tottenham Hotspur.

After a disagreement with Hearts over financial matters, Key was signed by Chelsea in 1905 for their first season in English football.

[7] The West London club's manager Jacky Robertson had been an international teammate of Key's three years earlier.

This biographical article related to association football in Scotland, about a midfielder born in the 1880s, is a stub.