Toplak played for NK Olimpija Ljubljana and Red Star Belgrade, with whom he had much success.

Toplak earned one cap for the Yugoslavia national team in 1956, but did not score a goal in that game.

After Yugoslavia, he went to the USA in 1967, where he managed the California Clippers from 1967 to 1968, Stanford University from 1969 to 1971 and the San Jose Earthquakes from 1974 to 1975.

He led the U21 side at the 1980 UEFA Euro U21 Championship where he got the team to the semi-finals.

In 1986 he was a co-manager of the Yugoslavia national team, this time alongside Ivica Osim.