 Birsa's career began at the age of five, when he started playing for ND Bilje, the village club of Bilje near Nova Gorica.As he was a talented player, he was soon transferred first to Primorje, then to Gorica at the age of 17.By the second season he was already the second best striker and one of the best in the Slovenian first league, scoring 29 goals for his home team, an outstanding goalscoring record for a midfielder.