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Rafael Nadal is a winner once again.

The second-ranked Nadal overcame a terrible start to beat Argentina's Juan Martin del Potro 1-6, 6-4, 6-1, 7-6 (0) on Sunday to clinch Spain's third Davis Cup title in four years.

Nadal's first title since winning his sixth French Open in June followed a run of below-par performances in which he acknowledged feeling less passionate about the sport as another long season took its toll. This victory gave Spain a 3-1 series lead, good enough for the country's fifth Davis Cup title overall.

Nadal showed flashes of that poor end-of-season run, but eventually settled into his usual dominant groove on clay. Del Potro also committed 64 unforced errors as Nadal earned his 20th straight victory since debuting in the competition in 2004 with a loss.

"I've never had the chance to secure the winning point of a Davis Cup. In the end it came down to me," said Nadal, who ensured Argentina remained the only nation to play in four finals without a victory.

Teammates Feliciano Lopez and Fernando Verdasco and captain Albert Costa were among those who enveloped Nadal after he dropped to the ground in celebration, while del Potro exited the arena in tears.

It was the third Davis Cup trophy for Nadal, who secured a point in the win over the United States as a teenager at the same Olympic Stadium in the 2004 final.

"It's a special feeling since you're playing at home in the last event of the year and it's to win the Davis Cup and all of the emotion and happiness that comes with being on the court," said Nadal, who missed the quarterfinal win in the United States before returning in the semifinals against France. "It's going to be impossible to repeat."

Not since the United States teams of the late 1970s and early 1980s has a country dominated the competition to such an extent.

"On home clay, they are probably one of the best teams in history," Argentina captain Tito Vazquez said after Spain stretched its record home winning streak to 21 series.

While Nadal has come to rule on clay since 2005 — losing only seven matches on the surface since then — he endured his most lopsided set loss in the competition as del Potro hit forehand winners at will to break serve four straight times.

Del Potro's pinpoint accuracy compounded Nadal's sluggish start and gave the visitors hope of becoming the first team since Australia 72 years ago to come back from a 2-0 deficit in the Davis Cup final.

While del Potro struggled on serve throughout, the Argentine overpowered Nadal with a laser-like forehand that contributed to his 44 winners.

But del Potro then started misfiring and Nadal found his rhythm to break back in the second game of the second set before finally holding serve.

"That was a very important moment," said Nadal, who routed Juan Monaco in his opening match. "After that game I felt like the match started for me."

Nadal steadied thanks to his strong backhand and eventually smashed a forehand winner to secure the set and send nearly all 23,000 fans into wild celebrations.

"I've never played in front of such a crowd before," said Nadal, one of only seven players to have completed a career grand slam of major titles.

Del Potro, who let slip a 2-1 set advantage in his opening singles loss to David Ferrer that took nearly five hours, sprayed his shots as nerves and fatigue appeared to creep into his game. Nadal ripped back-to-back forehand winners down the line to break early in the third set.

But a late comeback enabled Del Potro to break Nadal four times in the fourth set and send it to a tiebreaker. The Argentine then made four errors as Nadal raced ahead before securing victory without losing a point by hitting a forehand winner.

"He was dominating before that and I thought this might be the last set of the series, so I have to give it all," said Del Potro, the 2009 U.S. Open champion. "I played a good match despite losing. I felt that once again I was very close to winning."

Nadal and Ferrer are a combined 28-0 on clay in singles for Spain, which beat the Czech Republic in the 2009 final and opens its defense against Kazakhstan in February. Argentina, which also lost the 2008 final to Spain, will play Germany.

"It's not going to be easy to get us four together again," Ferrer said. "There are many talented players ready to step in. It's a lot of years together and each one has to manage his calendar so to find a series where we're all together again, and I don't see that happening."

Nadal said he won't play in the event next year so he can focus on defending his gold medal at the London Olympics.