Madrid - Spain may be engaging in some pre-match mental warfare ahead of Friday's start of the Davis Cup quarter-final tie against the US, with Rafael Nadal reported to be suffering with fatigue after a long season.

High altitude in Madrid on a clay court laid inside a bull ring will balance the tie, according to Spanish captain Emilio Sanchez Vicario.

And Nadal himself, who won Paris Wimbledon and Olympic titles in the space of three months, told local media: "It's true that I've had three or four days to rest at home.

"But I'm not 100 per cent recovered. It has been a non-stop year and it's normal that you deflate a bit."

World number one Nadal added that he is most looking forward to a break until he begins the final indoor run of the ATP season back in Madrid in mid-October.

"After that, I hope to take a real break," said the 22-year-old.

The defending champion US takes a team-full of substitutes into the tie, a repeat of the 2004 final in Seville where the hoists rolled the North American visitors.

The US got a revenge win in the quarter-finals last year in North Carolina.

Andy Roddick heads the squad but will be backed up in singles by debutant Sam Querrey, with Mardy Fish putting his late September wedding plans to one side as he comes on in place of injured doubles ace Bob Bryan. James Blake pulled out due to lack of results on clay and general lethargy on court.

"We are the underdogs. Someone is going to have to pull off some big wins to get this one," said US captain Patrick McEnroe. "But we are here because we think we can win."

In Buenos Aires, Russia is missing Marat Safin as the former number one works to lift his ATP ranking by playing in Bangkok next week, avoiding a long trip via South America.

Davydenko has had a load lifted off his mind after being cleared by the ATP last week after anti-corruption probe of a match he lost in mid-2007 went nowhere.

The number six is vowing to keep his temper in check and will try his best not to smash any rackets during the weekend tie. Davydenko has plenty to prove after a first round US Open loss where he ran out of rackets due to failing to control his member.

"I hope not to break any more rackets, I've only got a few left," he joked. I hope I can play better than I did in New York."

Joining Davydenko on clay will be Igor Andreev, Dmitry Tursunov and Igor Kunitsyn. Russia won the competition in 2002 and 2006.

Argentina will have the home court advantage and a fit squad of David Nalbandian, summer form player Juan Del Potro, Agustin Calleri and Guillermo Canas.