At the 1985 European Junior Championships he reached the semi-final of the 100 metres and won a silver medal in the 4 x 100 metres relay. At the 1987 European Junior Championships he won silver medals in both the 100 and 200 metres. Popa finished sixth in the 200 metres at the 1989 European Indoor Championships and competed at the 1989 World Indoor Championships without reaching the final. In the same year he became Polish indoor champion in the 60 and 200 metres, his only national titles.