Novak Djokovic, less than a week following his U.S. Open championship, was given the opening-match duty for Serbia in this weekend\'s Davis Cup semifinal. Djokovic and the Serbs are the defending Davis Cup champions and will go against Argentina in a best-of-five series on an indoor, hard court in Belgrade, Serbia. The winner moves to the Davis Cup finals Dec. 2-4 against either Spain or France. Djokovic is No. 1 in the world in a year in which he\'s won 64 of his 66 matches. He\'ll face David Nalbandian, ranked 74th, in Friday\'s first singles match. The second match has Janko Tipsarevic, who was a U.S. Open quarterfinalist and it ranked 13th in the world, against 17th-ranked Juan Martin de Potro. Tipsarevic is scheduled to team with Nenad Zimonjic for Saturday\'s doubles match against Argentines Juan Ignacio Chela and Juan Monaco. Djokovic was also penciled in for Sunday\'s first reverse singles match when he\'d go against del Potro. The final match has Tipsarevic playing Nalbandian. The victory last year was the first Davis Cup win for Serbia, although the Serbians were part of a 1964 Yugoslavian team that defeated Argentina in their only previous Davis Cup meeting. Argentina has never won the Davis Cup but advanced to the finals in 1981, 2006 and 2008.