Daunting task for defending champion United States

Nine of the world's top 10 players, including the quartet of Rafael Nadal, Roger Federer, Novak Djokovic and Andy Murray, are in action this weekend in the Davis Cup, one of the few high-profile events left in the season now that the Grand Slams are done with.

Both world group semifinals are blockbusters, and much drama figures to unfold in the world group playoffs. Here's a preview of the all the matchups:

U.S. vs. Spain, Madrid, clay, outdoors
Facing Spain at full strength was always going to be daunting for the defending champs. Now that a burned out James Blake and injured Bob Bryan have withdrawn, a win for the visitors would go down as one of the biggest upsets in tournament history, given that Nadal, arguably the best clay-courter of all time and the world No. 1, is also starting for Spain.

(The Miracle on Clay?)

To have any realistic chance of advancing, Andy Roddick, carrying a heavy load as usual, needs to overcome the slumping David Ferrer on the opening day. Nadal begins against Davis Cup rookie Sam Querrey, who played him tough at the U.S. Open.

Prediction: Spain

Russia vs. Argentina, Buenos Aires, clay, outdoors
Argentina, still seeking a first title, lost to Russia in a thrilling 2006 final that went down to the wire in Moscow. Expect plenty of intrigue in Buenos Aires, too.

Both No. 1's -- Argentina's David Nalbandian and Russia's Nikolay Davydenko -- are slumping. Nalbandian, who does raise his game in the competition, has his hands full against Igor Andreev on Friday, and Davydenko starts against the in-form Juan Martin Del Potro, although the latter prefers hard courts. Marat Safin, the hero two years ago, skipped the series to focus on his tour ranking.

If Argentina prevails, they get yet another home tie -- their fourth this season -- in the final.

Prediction: Russia

World Group Playoffs

Belgium vs. Switzerland, Lausanne, hard, indoors
Federer, on a high following his success at the U.S. Open, doesn't play Davis Cup too much anymore, but he's there at crunch time: His appearance against Belgium marks the fourth straight year the 27-year-old has turned up in the playoffs, with Switzerland victorious twice in the previous three.

"I feel fine," Federer said. "I haven't played a match in 10 to 12 days and am ready to go."

He might be feeling nostalgic. Federer's first road Davis Cup series came against Belgium in 1999, also when the nations last met, and he lost both his singles matches, to Xavier Malisse and Christophe Van Garsse.

Federer and Stanislas Wawrinka, doubles gold medalists in Beijing, are scheduled to team up again Saturday.

"If we win one point, it will be a miracle," Belgian No. 1 Steve Darcis said. "If we win three, it's three miracles."

Prediction: Switzerland

Serbia vs. Slovak Republic, Bratislava, hard, indoors
The last time Djokovic took part in the Davis Cup, he cited illness and pulled out of the fourth match in this year's first round against Russia while leading Davydenko two sets to one, handing the host the series in February. Seven months later in New York, as we all know, his health took center stage again.

Djokovic is down for playing three matches this weekend, but if, for some reason, he can't compete, Janko Tipsarevic and the improving Viktor Troicki provide ample depth against the 2005 finalist, led still by the aging Dominik Hrbaty.

"We might be seen as the underdog, but I can assure you that we have no intention of being in white-flag mood," Slovak captain Miloslav Mecir said.

Prediction: Serbia

Austria vs. Great Britain, Wimbledon, grass, outdoors
Hanging with the likes of Nadal and Federer on the final weekend in New York, how will Murray, the U.S. Open finalist, react now that he's in the company of, uh, Alex Bogdanovic and Ross Hutchins, among others?

Austrian lefty Jurgen Melzer, who blew a two-set lead to Murray at Flushing Meadows a few weeks ago, had similar thoughts.

"After playing such a great Grand Slam, I imagine it would be tough to get your head clear and focus on the next [match]," Melzer said.

Mind games aside, Murray is favored to win both his singles tussles, and Bogdanovic, his No. 2, is expected to lose twice.

That brings it down to the doubles, where both teams are strong.

Prediction: Austria

Australia vs. Chile, Antofagasta, clay, outdoors
Antofagasta, in case you're wondering, is a beach resort about 700 miles north of Santiago, the capital. So, that's one bright spot for the Aussies.

Minus the injured Lleyton Hewitt, captain John Fitzgerald's roster is the most inexperienced in the country's storied Davis Cup history, and there were rumors wonder-kid Bernard Tomic, 15, would actually play Friday.

Fitzgerald ultimately chose Peter Luczak as the No. 2, behind big-serving Chris Guccione. Chilean No. 1 Fernando Gonzalez is 16-1 in home Davis Cup encounters.

Prediction: Chile

Brazil vs. Croatia, Zadar, hard, indoors
There's no Guga, but Brazil has some name recognition: No. 1 Thomaz Bellucci, a go-for-broke baseliner, tested Nadal at this year's French Open; Thiago Alves showed some spunk against Federer in New York; and the tandem of Andre Sa and 6-foot-8 Marcelo Melo is eighth in the doubles standings.

With top prospect Marin Cilic out due to facial paralysis, 6-foot-10 Ivo Karlovic and Mario Ancic, returning from a recurrence of mono, got the nod in singles for the Croatians.

"I'm practicing for two weeks now, after a spell in the mountains to get my strength back," said Ancic, never averse to hard work.

Karlovic, bizarrely, has lost six in a row in the competition.

Prediction: Croatia

India vs. Romania, Bucharest, clay, outdoors
With a population of more than one billion people, there's always suitable interest in tennis in India, even if the country, mad about cricket, hasn't produced a notable men's singles star for decades.

Could Somdev Devvarman emerge? The 23-year-old won the NCAA men's singles championship two years in a row with the University of Virginia -- topping John Isner last year -- and has impressed in the pro ranks this season, claiming a Challenger, three Futures events and reaching his first top-tier quarterfinal. This month, he took Nicolas Almagro to three sets on clay in, ironically, Romania. He'll have the experienced Leander Paes and Mahesh Bhupathi as two of his teammates as India seeks a spot in the world group for the first time since 1998.

"What Somdev in particular has done in recent months is a fabulous achievement," said Paes, who made his Davis Cup debut in 1990.

The home team is leaning on Victor Hanescu, a former French Open quarterfinalist who won his first title in July.

Prediction: India

South Korea vs. Netherlands, Apeldoorn, clay, indoors
South Korea's first Davis Cup world group series in 21 years ended in defeat in Germany in February. Hyung-Taik Lee ensured a meaningful match on the final day by winning his singles opener, but he needs to reverse his current slump. At a career-high 36th in August 2007, the 32-year-old has lost his past six matches on the ATP circuit to slide out of the top 150.

Home hopes, however, took a huge blow when No. 1 Robin Haase had to withdraw because of a knee injury, leaving singles duty to Thiemo De Bakker and Jesse Huta Galung, both outside the top 180.

"It would be a surprise if we were to qualify for the world group with such a young and inexperienced squad," said Dutch captain Jan Siemerink.

Prediction: Netherlands

Peru vs. Israel, Ramat Hasharon, hard, outdoors
Israel's world group appearance in February was its first in 14 years, while Peru advanced to the elite level for the first time; one of the two is assured a top-16 place for the second straight season.

Although he's struggled in the pro ranks in 2008, Dudi Sela, a pint-sized 5-foot-9, led Israel to the world group with victories over Gonzalez and Massu at the same venue last year. Peruvian No. 1 Luis Horna is probably also happy to be representing his country.

Horna is 9-2 in his past 11 Davis Cup matches but has dropping eight in a row at the top tier. Usually the favorites in doubles, Israel is without the injured Jonathan Erlich, one half of the Erlich-Andy Ram partnership. Horna, to remind, won the French Open doubles with Uruguayan Pablo Cuevas.

Prediction: Israel

Ravi Ubha is a frequent contributor to ESPN.com.