Born in Topola, Duljaj was spotted by Partizan in 1990. He initially traveled to Belgrade to attend training sessions for several years, before permanently relocating to the capital city. In the 1997–98 season, Duljaj was promoted to the main squad, appearing in five league games and scoring once. He became a first-team regular in his third year as a senior, collecting 41 appearances in all competitions while scoring one goal in the league. Over the course of the next three seasons, Duljaj was an irreplaceable member of the team that won one national cup and back-to-back championships in 2002 and 2003. He subsequently helped the side progress to the group stage of the 2003–04 UEFA Champions League, eliminating Newcastle United in the last qualifying round. In February 2004, Duljaj was transferred to Shakhtar Donetsk. He penned a five-year contract with the club, rejoining his former Partizan teammate Zvonimir Vukić. Over the following seven seasons, Duljaj won four Ukrainian Premier League titles, two Ukrainian Cups, two Ukrainian Super Cups, and one UEFA Cup. He amassed a total of 195 appearances in all competitions and scored six goals. In July 2010, Duljaj signed with fellow Ukrainian club Sevastopol. He spent four seasons with the side, two in the top flight and two in the second tier, before retiring from the game.
International career
Duljaj was capped for FR Yugoslavia at under-18 and under-21 level. He also represented the country at the Millennium Super Soccer Cup in early 2001. Led by manager Ilija Petković, Duljaj appeared in all five of his team's games and scored two goals, helping the side win the tournament. However, these caps are not officially recognized by FIFA. Previously, Duljaj made his full international debut for FR Yugoslavia in a 2–1 friendly loss against Romania on 15 November 2000. He went on to represent his country on 47 occasions, being a member of the team at the 2006 FIFA World Cup.
Post-playing career
In the summer of 2016, Duljaj joined the coaching staff at Shakhtar Donetsk, becoming an assistant to manager Paulo Fonseca. In December 2019, it was announced that Duljaj would be joining Savo Milošević's staff at Partizan.
Personal life
Duljaj has two brothers, Joakim and Nenad. Together they run the Duljaj Football Academy in their hometown of Topola.
