 He signed a professional contract at the age of 17 after passing through every age level at the club, making his First League debut during 1968–69 season.He was the Yugoslav First League joint topscorer in 1970–71 season alongside Hajduk's Petar Nadoveza.Particularly notable during this season was Janković's performance in an away league match versus Red Star Belgrade at Marakana when he scored 4 goals - the game ended 4–1 for Željezničar.