Irishman Charles O'Hagan was the team captain from 1906-1910. He was also the first Aberdeen player to be capped for his country. He also went on to be the manager of Sevilla later on in life. He had a very interesting life.
https://thesefootballtimes.co/2017/11/01/the-mysterious-career-of-charles-ohagan-sevillas-first-foreign-manager/