On 27 September 1982, Koller scored at Santiago Bernabéu, opening the score for FC Baia Mare in a European Cup Winners' Cup second leg match against Real Madrid. At that time, the Romanian team was playing in Divizia B, the second division. Eventually, Real Madrid won by 5 goals to 2.[6][7]
He retired from football in 1983, aged only 30, to become vice-president of FC Baia Mare and then between 1990 and 1996 he was president and owner of the club.[2]