MADRID (Reuters) - Davis Cup debutant Sam Querrey faces a baptism of fire in Friday's semi-final opener after drawing world number one Rafael Nadal on clay in front of 21,000 spectators in Madrid's Las Ventas bullring.

"I can go out there and make faces but there's not much more I can do," Querrey told reporters after the draw.

"I have to play aggressive, connect with some big serves and dictate the points," added the 20-year-old, who lost 6-2 5-7 7-6 6-3 to Nadal in the fourth round at this year's U.S. Open.

Querrey, who at two metres towers over Nadal, was called into the squad by U.S. captain Patrick McEnroe after an exhausted James Blake withdrew, which further stacked the odds against the champions.

"I actually think it's good that Sam's playing first," said McEnroe. "He doesn't have to sit in the locker room listening to 20,000 people whistling".

In the second match of the day, American Andy Roddick, the world number eight, plays fifth-ranked David Ferrer and the Spaniard forecast a difficult match.

"The key is going to be returning the ball. It's going to be a long game," said the Valencia-born 26-year-old.

PUBLIC SPAT

The host team's opposition to playing in Madrid -- with its faster courts at 660 metres above sea level -- has led to a public spat with Spanish tennis federation chairman Pedro Munoz.

However, Roddick played down the effect of altitude on the specially-built clay court.

"It's not a slow clay court but it's not the fastest I've seen either," said the big-serving American who during his career has won two out of three of his clay court matches and five titles on the red dust.

"If I'm playing well, I feel good on clay. I've been hitting the ball really well this week, I feel good".

Saturday's doubles had offered the United States its best chance of a point but Spain's Fernando Verdasco and Feliciano Lopez have a better chance following injury to Bob Bryan -- one half of the world's top-ranked doubles pair.

With Bryan's late withdrawal, twin brother Mike will play Saturday's match with U.S. Open quarter-finalist Mardy Fish.

Mike Bryan said despite not playing with anyone but Bob in six years, training was going well as he and Fish worked on routines and signals. "Bob should be worried," he joked.

Roddick will play Nadal in the first of the reverse singles on Sunday -- the Spaniard has a 3-2 career record against him -- followed by Querrey against Ferrer as Spain seek to repeat their 2004 victory over the U.S. in Seville.

The winning team will play Argentina or Russia in the final.

(Editing by Ken Ferris)