Mudrinski signed for Red Star Belgrade in August 2012. In advance of his promotion to the club, he had chosen the number 91 to represent the team's historic win against Olympique Marseille in the 1991 European Cup Final. On 2 September 2012, he scored a hat-trick against Radnički Niš on his debut for Red Star, becoming the first player in club history to do so. After he played in postponed first fixture match against Javor Ivanjica, Mudrinski collected 16 caps in 15 fixtures in the first half of the season. However, by the end of the 2012–13 season, Red Star coach Ricardo Sá Pinto told Mudrinski that he would not be relying on him in the following season.