After starting his career with Pro Gorizia in 1939, Blason made a name for himself with Triestina, making his debut in the Italian top–flight during the 1945–46 season.

He was one of the main figures during the team's historic second–place finish in the league during the 1947–48 season, behind the famous Grande Torino side.

[1] Blason took part at the 1950 FIFA World Cup in Brazil with Italy, and made his only international appearance during the tournament, which came in a 2–0 win over Paraguay on 2 July.

He was capable of playing in several defensive roles, and often played as a full-back in the WM system or sistema, which at the time was similar to the role of the modern centre-back; however, he was later also used as a sweeper, and is credited by Andrea Schianchi of La Gazzetta dello Sport with being the first official libero in Italian football when he was deployed in this role with Inter under manager Alfredo Foni, and subsequently at Padova under manager Nereo Rocco; in this position, he was often the deepest player on the team positioned behind the back-line, who would clear balls away from the penalty area.

Although he was primarily known to be a traditional sweeper, whose main role was to clear balls away, he was also known for his ability to start counter-attacks with long passes.