MADRID, Spain — The U.S. reign as Davis Cup champion ended Sunday, with an ailing Rafael Nadal beating Andy Roddick in a straight-sets victory that sent Spain to the final for the sixth time.

The top-ranked player won 6-4, 6-0, 6-4 on a clay court at the Las Ventas bullfighting arena, giving Spain an insurmountable 3-1 lead in the best-of-five format. Spain will play for the title against Argentina or Russia. The Argentines lead that semifinal 2-1 in Buenos Aires.

"It's one of the nicest sensations you can experience in your career," said Nadal, who dropped to his knees and pumped his fists after the victory.

Nadal said after the match he nearly didn't play because an MRI scan Saturday showed a strained buttock muscle.

He broke Roddick five times, saved all seven break points and served eight aces. He won on his sixth match point by slicing a backhand winner across court from deep behind the baseline.

Nadal, a master on clay and a four-time French Open champion, picked Roddick apart with an array of passing shots, ground strokes and serves before a boisterous crowd of nearly 21,000.

Roddick was blanked in a set for the first time in 22 Davis Cup series. Nadal also beat Roddick in the 2004 final at Seville to help Spain capture its second Davis Cup title.

"I don't think you could draw up a tougher scenario than playing Nadal away in front of this crowd," Roddick said.

Roddick, a former U.S. Open champion, fell to 0-5 in must-win Davis Cup matches and 0-4 against players ranked higher than he is. The 26-year-old American, known for his big serve, had only eight aces with four coming in the next-to-last game.

"He's the best clay-courter of all time and I'm not that good of a clay-courter," Roddick said. "He wasn't leaving any balls short; he was kind of going for his shots."

Roddick ventured to the net, but the strategy did not yield much against an opponent as savvy as Nadal.

"It was high risk, high reward," he said. "I don't think there was much of a chance for me to sit back and trade punches with him from the baseline."

Nadal and David Ferrer led Spain's sweep of opening singles Friday. The U.S., a 32-time Davis Cup champion, earned its point from Saturday's doubles victory by Mardy Fish and Mike Bryan.

In the other reverse singles Sunday, Feliciano Lopez replaced Ferrer to play Sam Querrey in a now meaningless match.

Nadal, who has only lost twice in his past 117 clay matches, first troubled Roddick in the fifth game of the first set, but the American saved that double-break chance.

The Spaniard set up a triple-break chance in the eighth game with a backhand passing shot after a volley exchange. He then hit a forehand down the line to break for a 4-3 lead. The crowd became charged up after Nadal rolled on the clay in vain to reach a drop shot.

In the 10th game, Roddick had a double-break chance after Nadal hit long. Roddick flubbed the first one before Nadal delivered a forehand slam at the net, then closed things out with his third ace.

Roddick was exasperated after a 12-shot rally in the third game of the second set finished when Nadal hit a backhand into the corner. A return winner set up a double-break chance, which Nadal converted with a backhand.

Roddick had another break chance in the sixth game thanks to a well-crafted drop shot, but Nadal caught the American going the other way with a volley. Nadal closed the second set as he did the first — with an ace.

Roddick finally won a game to open the third set and then set up a triple-break chance in the second game. But Nadal hit a winner before Roddick sent two shots down the line wide. He let out a roar as Nadal saved again.

Roddick won about half as many first-serve points as Nadal, and was soon down 2-1 after hitting out to drop serve.

U.S. captain Patrick McEnroe offered only a chuckle to Roddick during the changeover with the American trailing 3-2 and the crowd chanting Roddick's name.

Nadal was unable to break Roddick one last time in the ninth game. The American saved five match points before Nadal eventually clinched the victory.