His favourite part of the career was the amateur one. He partecipated in three hundred fourteen matches as amateur. He won two hundred ninety-five times and lost thirteen times, while six matches ended in draw definition. His wins by surrender of the opponent, which were quite a lot, are not included.

He was 186 cm tall, was a southpaw stance boxer.

He started boxing in the middleweight division, while in November 8, 1970, he started boxing in the light-heavyweight division.

In eight years and eight months (March 1970 – December 1978) he lost, on points, only one unimportant match.

In eighteen matches for the Jugoslav national boxing team, he won seventeen times.

He was the junior Champion of Croatia in 1966.

He was the Champion of Croatia in 1967 and 1968.

He won the international tournament Olympic Hopes in Budapest in 1967.

He was eight-time Champion of Jugoslavia (1967 – 1970 in the middleweight division, 1971 – 1974 in the light-heavyweight division).

He was five-time Champion of the Balkans (Varna 1970 in the middleweight division, and Titograd 1971, Ankara 1972, Athens 1973, Constanta 1974 in the light heavyweight divisioin).

He won the international tournament Golden Glove in Belgrade in 1967 after he had defeated Bogoljub Kahriman by tko in the first round.

At the 1968 Mexico City Olympic Games, he took fifth place after he had defeated Lahcen Ahidous of Marocco by uninimous decision, and in the next match a Dutch boxer Jan van Ipselen on points. In the quarterfinals he lost against a British boxer Chriss Finnegan on points, who later turned out to be a gold medalist.

At the 1969 European Championships held in Budapest, he won a silver medal. In the first match he defeated the German boxer Ewald Yarmer by unanimous decision, in the next one the Polish boxer Janusz Gortat on points, and in the semifinals Reima Virtanen of Finland by unanimous decision. In the finals he lost on points against the Russian boxer Vladimir Tarasenko from the Soviet Union.

He won the international tournament Golden Glove in Belgrade in 1969 after he had defeated the Russian boxer Vladimir Tarasenko from the Soviet Union by unanimous decision.

In 1971 he became the European Champion in Madrid. In the first match he defeated Tony Roberts from Wales by unanimous decision, then the Ukrainian boxer Vladimir Metelev from the Soviet Union by tko in the second round. In the quarterfinals he defeated on points Janusz Gortat from Poland while in the semifinals Horst Stump from Romania by unanimous decision. In the finals he beat the German boxer Ottomar Sachse by unanimous decision, and became the first Jugoslav boxer to win the gold medal in the European Championship.

At the 1972 Munich Olympic Games, he won the gold medal. In the first match he defeated Noureddine Aman Hassan from Chad by tko in the second round, then the Hungarian boxer Imre Toth also by tko in the second round. In the quarterfinals, he won against Miguel Angel Cuello from Argentina by walkower. In the semifinals he defeated Janusz Gortat of Poland by unanimous decision. In the finals, after one counting in the first round, the German referee Joachim Wolff counted tree times to a Cuban boxer Gilberto Carillo in the second round and stopped the match. He became the first Jugoslav boxer to win the Olympic gold medal.

He again became the European Champion in Belgrade in 1973. In the first match he defeated Mike Imrie of Scotland by ko in the first round, then Billy Knight of England by tko in the third round, and in the semifinals the Russian boxer Oleg Korotayev from the Soviet Union by tko in the second round. In the finals he defeated Janusz Gortat of Poland by unanimous decision.

At the inaugural World Amateur Boxing Championships held in Havana in 1974, he won the gold medal. In the first match he defeated the Romanian boxer Constantin Dafinoiu on points. In the quarterfinals, in front of fifteen thousand spectators, he fought against the Cuban boxer Gilberto Carillo. In the first round Mate went down twice, and after that the Cuban once. In the second round Carillo went down again. In the third round the Cuban boxer went down two times, and Mate won the fight on points. This match was proclaimed the most dramatic match ever of the World Amateur Championships. In the semifinals he won the German boxer Ottomas Sachse by unanimous decision, while in the other semifinals the Russian boxer Oleg Korotayev from the Soviet Union won the USA boxer Leon Spinks by tko in the third round. In the finals he defeated Korotayev by tko in the second round, and became the first ever light-heavyweight World Amateur Champion.