He started his senior pro career with OFK Beograd in 1981 at only 16 years and 16 days of age (at that time the youngest ever in the Yugoslav First League), before moving on to Red Star Belgrade in 1983 where he stayed until 1990.

[1] He played several matches for Beşiktaş in the 1992-1993 season and scored 4 goals, before returning to the Netherlands with SC Cambuur.

Mrkela holds distinction as the youngest player ever to play for SFR Yugoslavia national squad.

He was only 17 years and 130 days old when he made his national team debut on 17 November 1982 during a Euro 1984 qualifier versus Bulgaria in Sofia.

However, despite a lot of early promise, Mrkela would go on to make only 5 national team appearances, scoring 1 goal.