Chile's Fernando González in the final to win the gold medal. With the win, Nadal finally clinched the world No. 1 ranking on 18 August, ending Federer's record four-and-a-half-year reign at the top. At the US Open, Nadal was the top-seeded player for the first time at a major. He did not lose a set during his first three matches, defeating qualifiers in the first and second rounds and Viktor Troicki in the third round. In the semifinals, he lost to Andy Murray. Later in the year in Madrid, Nadal helped Spain defeat the United States in the Davis Cup semifinals. At the Madrid Masters, Nadal lost in the semifinals to Gilles Simon. However, his performance at the event guaranteed him the year-end No. 1 ranking, making him the first Spaniard to finish a season as such in the Open Era. Two weeks later at the Paris Masters, Nadal reached the quarterfinals, where he withdrew because of a knee injury. The following week, Nadal announced his withdrawal from the year-ending Tennis Masters Cup in Shanghai, citing tendinitis of the knee. On 10 November, Nadal withdrew from Spain's Davis Cup final against Argentina, as his knee injury had not healed completely. 2009: Australian Open and Davis Cup titles Nadal's first ATP Tour event for the season was the Qatar Open, where he lost in the quarterfinals to Gaël Monfils. Nadal also entered and won the tournament's doubles event partnering Marc López, where they defeated the No. 1-ranked doubles team of Daniel Nestor and Nenad Zimonjić in the final. At the 2009 Australian Open – Men's singles, Nadal won his first five matches without dropping a set, before defeating Fernando Verdasco in the semifinals in the second longest match in Australian Open history at 5 hours and 14 minutes. This set up a championship match with Roger Federer, their first meeting in a hard-court major. Nadal defeated Federer in a five-set final to earn his first hard-court major singles title, and become the first Spaniard to win the Australian Open. At the ABN AMRO World Tennis Tournament in Rotterdam, Nadal lost in the final to second-seeded Andy Murray in three sets. Although this knee problem was not associated with Nadal's right-knee tendonitis, it was serious enough to cause him to withdraw from the Dubai Championships a week later. In March, Nadal helped Spain defeat Serbia in a Davis Cup World Group first-round