In 1936 Lešnik started playing for Građanski Zagreb, the club where spent most of his career.
[3] He clinched two titles with Građanski in 1937 and 1940, and one of his most famous club matches occurred in spring 1937 against BSK in Belgrade in which Lešnik scored a hat-trick in the first seven minutes of the game.
[4] After World War II, Građanski was disbanded by the communist Yugoslav authorities, and Lešnik finished his career with the newly formed Dinamo Zagreb.
Lešnik made his debut for Yugoslavia in a May 1937 friendly match away against Hungary and earned a total of 10 caps, scoring 4 goals.
Nevertheless, Lešnik was famed for his sudden sprinting bursts, usually close to goal, and his agility and execution were unmatched by any Dinamo player until generations later, by strikers such as Dražan Jerković and Davor Šuker.