Alex was born in Springburn in Glasgow on 17th September 1944 and was a product of the famed Drumchapel Amateurs alongside cousin Jim Forrest. Both went on to gain Scottish schoolboy caps before joining Rangers as 15 year-olds. Alex made 150 appearances for the Ibrox club in nine seasons before Eddie Turnbull signed him in the close season of 1969.

Originally an inside forward, Alec was used in a variety or roles and by the end of his Aberdeen career he was converted in to a right back, initially taking on that role in the club tour of Canada in 1972 and on a more permanent basis from Henning Boel who was out for a long spell with a knee injury.

Alex made his debut against Dunfermline in a 2-2 draw that saw him once again teamed up with Jim Forrest. It was his first game against his old club at Ibrox that Alex was injured in a clash with John Greig. The injury led to complications and ultimately left him out of the Dons successful 1970 Scottish Cup winning side.

Alec had the rare distinction of being the last player that Aberdeen bought from Rangers and he went on to make 149 appearances for the club, scoring 15 goals in the process. He was a member of the squad that pushed Celtic all the way in the title challenge of 1971 and it was Willoughby's goal against the Parkhead side at Pittodrie in April of that year, in the match that was billed as a league decider that helped the Dons to a 1-1 draw. Alex left Aberdeen in 1974 to play in Hong Kong, Australia and South Africa.

His name will live in on in footballing circles in this area after Alex provided the Willoughby Cup which is contested for annually by the primary schools in Aberdeen City.