PARIS (AFP) - Rafael Nadal and Roger Federer swap their gripping personal rivalry for Davis Cup duty this weekend with the two superstars having dramatically different ambitions. Nadal leads Spain into a semi-final clash against defending champions USA in a Madrid bullring with a final date with either Argentina or Russia in the offing. Federer, fresh from his 13th Grand Slam triumph at the US Open, hopes to guarantee Switzerland a place in the 2009 World Group with a home tie in Lausanne against Belgium. World number three Novak Djokovic is also on national service leading Serbia into their play-off against 2005 runners-up Slovakia in Bratislava. Nadal faces Sam Querrey in the opening rubber with David Ferrer next on against former world number one Andy Roddick. "I would have liked to rest a little longer after the US Open but I am ready to make one more huge effort as the Davis Cup is my main goal for the rest of the year," said Nadal who was beaten by Britain's Andy Murray in the US Open semi-finals. "I think I'll get a second wind here.Roddick also played down any thoughts that Nadal's fatigue would be a factor. "Having 22,000 of his closest friends here will eliminate any fatigue. He's too much of a competitor," said the American. Federer is keen to put the record straight in Lausanne where he will shoulder the burden with Olympic Games doubles gold medal-winning partner Stanislas Wawrinka.The Swiss lost at this stage last year to the Czech Republic and were also beaten 3-2 the last tie they played Belgium in the 1999 quarter-finals. Swiss number one Marc Rosset was missing because of illness while a 17-year-old Federer lost both his singles. "I don't have good memories of that tie and have been waiting for a long time to play Belgium again," said Federer who plays close friend Kristof Vliegen on Friday with Wawrinka opening against Steve Darcis. Djokovic is expected to play all three days in Bratislava against Slovakia. He will face veteran Dominik Hrbaty in Friday's opener while Janko Tipsarevic tackles Lukas Lacko in the second rubber. "I know what our mission here is, and if I have to play first I will. I realize that Dominik is an illustrious player, almost invincible on home soil, but we are all pros and should be used to crowd as well," said Djokovic. World number four Andy Murray leads Britain's challenge against Austria at Wimbledon and will tackle Alexander Peya in the second rubber once Alex Bogdanovic has taken on Jurgen Melzer.