[2][3] Dunlop was born in Annbank, South Ayrshire, and played for his hometown club (taking part in a trial for the Scotland national team in 1890)[4] before coming to England to sign for Sunderland at the start of 1893.
He was the uncle (though only two years older) of his new club's star forward Jimmy Miller,[5][6] while another former Annbank player, defender Robert Smellie, was also in the Sunderland side (he and Dunlop were teammates in the team's run to the quarter-finals of the 1891–92 Scottish Cup).
[7][8] Dunlop made his debut for the Wearside club on 28 January 1893 in a 4–2 home win against The Wednesday, and played a few more games at the end of the 1892–93 season once the League title was secured.
[9] He also played on the winning side in a post-season friendly match against Scottish champions Heart of Midlothian, dubbed by some the "1895 World Championship".
[10] Dunlop returned to Scotland in 1899 to join Rangers, and played six Division One games in the 1899–1900 season – in each case covering for one of the regular half-backs, Neilly Gibson, Bobby Neil and Jacky Robertson – plus a few more games in other competitions, in a couple of which Jimmy Miller also played.