Grüner made his debut in the Freestyle World Cup on November 30, 2002 and in Tignes took second place behind the Czech Tomáš Kraus at the first ski cross World Cup race in history . Another podium followed in the winter of 2003/04. At the start of the 2004/05 season, Grüner won the race in Saas-Fee on October 23, 2004 , which was synonymous with his only World Cup victory. Three more podium places followed, so that he finally finished just behind Kraus in second place in the ski cross discipline and was third in the overall World Cup. At the 2005 World Championships in Ruka , he finished 9th. In the winter of 2005/06 he achieved five placements among the top ten, and at the end of the season he retired from top-class sport.
Austria