Olympic gold the pinnacle of the sport: Nadal By Sarah Morris MADRID (Reuters) - Winning a gold medal for your country at the Olympic Games is the greatest achievement in tennis, world number two Rafa Nadal said on Friday, while also leaving the door open to a possible return to Spain's Davis Cup team in September. After his triumph in Beijing four years ago, Nadal will be chasing a second Olympic singles gold in London, when the event in July and August will be staged on the grass courts of Wimbledon's All England Club. In an interview with Reuters, the 25-year-old said that for him personally the Olympics ranked above the four grand slams in prestige. "The Olympic Games is very special for many reasons and in my opinion the biggest one because you are representing your country," Nadal said as he prepares for the Madrid Masters event starting next week. "You have the feeling that you are with all the Spanish sportsmen representing our country," added the Mallorcan, who beat Chile's Fernando Gonzalez to win the gold in 2008. Nadal's pride in representing the Iberian nation was evident as he helped them to a fifth Davis Cup triumph in last year's final against Argentina but he said afterwards he would not play in the competition in 2012 due to the congested calendar. However, he is now not ruling out returning to the team for September's World Group semi-final at home to United States, when the holders will continue their bid for a fourth title in five years. "There remain a lot of months, a lot of important events, so I cannot think about it when I am here in Madrid preparing for an important tournament like this one," Nadal said. So let's see how the season goes and I will wait until that date (before deciding). Nadal's season was disrupted in March when he was forced to pull out of his Sony Ericsson Open semi-final against Andy Murray in Miami due to a recurrent knee problem. He returned to fitness in time to claim a record eighth straight Monte Carlo Masters on his favored clay last month and went on to become the first player to win two events seven times at last week's Barcelona Open. "I am okay," he said when quizzed about the injury. "I've played two weeks back to back in Monte Carlo and Barcelona with no problems," he added. That's very important for me, a lot of confidence for my mind. And the answer: the knee is now perfect. Nadal, a 10-times grand slam singles champion, is due to begin the defense of his French Open title in Paris at the end of this month. Writing by Iain Rogers, editing by Mark Meadows