At full strength, the American Davis Cup squad would have little chance of beating the Spanish team in this weekend’s semifinals. The Americans, who are defending champions, have the talent to win, as they proved last year when they defeated Spain on their way to their first title since 1995. But that was on a hard court. On clay in Madrid, Spain effectively begins the contest with a 2-0 lead, unless Rafael Nadal injures himself or consumes a large helping of spoiled food. Nadal lost four games in the French Open final this year against Roger Federer, the second-best clay court player in the world. He might beat the Americans right-handed (it is, after all, his natural hand).

Even without Nadal, the Spaniards would have the advantage, as David Ferrer, Fernando Verdasco, and Nicolas Almagro are superior clay court players to anyone on the American squad. Now for the bad news: James Blake, the second-best American player, and Bob Bryan, who clinched last year’s title with his brother Mike, won’t be in Madrid. Blake is wiped out from a long season and needs a rest. Bryan has been playing with an injured shoulder since Wimbledon. Without them, the Americans — Andy Roddick and Sam Querrey at singles, along with Mardy Fish (whose wedding is a week away) and Mike Bryan at doubles — face their most difficult challenge since Patrick McEnroe took command of the team nearly eight years ago.

The only thing the Americans have going for them is the fact that the Spanish players do not approve of their federation’s decision to play in Madrid (the players lobbied against it earlier in the year). In practice this week, Nadal has complained that the balls are flying uncontrollably off his racquet, thanks to the high altitude. If that decides this contest, however, then the Spaniards don’t deserve to play Davis Cup at all next year. Make no mistake: If the Americans win this weekend, it would be a victory so shocking that it might dwarf any other in American Davis Cup history.

Nonetheless, some good ought to come from a weekend that almost certainly will end in defeat. What better way for Querrey — the most promising player of the generation to follow Roddick — to learn the ways of the Davis Cup than from inside a converted bullring in Spain, with 20,000 people screaming for his hide and Nadal standing across the net, when the two play first on Friday? Down the road, McEnroe will depend on Querrey for the team’s success, or at least to bridge the gap between Querrey’s generation and the next wave of American players, the best of whom is only 16 years old. Fish is not a long-term solution for doubles, but it will do the team some good to recall a time when the Americans didn’t have a duo as talented, and as reliable, as the Bryan twins. The twins are 30 now and might not maintain their dominance for too many more years, though there’s a decent chance they’ll be better than any other American team for at least another five years. Unlike McEnroe, every other Davis Cup captain has to mix and match in doubles. McEnroe might be in their shoes sooner than he would hope.

All this bad news probably sounds defeatist or glum to you, but I assure you that’s not my intention — there’s no point in pessimism. This is the reality of the Davis Cup today. There are more countries with talented players and fewer chances to dominate. Russia, which plays Argentina in the other semifinal this weekend, has enough talent to win the Davis Cup every year, but the depth of competition is such that it has won twice since 2002. It’s no shame, then, for the Americans to fail to defend their title. If the American team does anything this weekend that shows a winning formula for the future, raise a glass in honor of the Spaniards and call the weekend a success.

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America versus Spain will get much of the attention this weekend, but the slight favorites to win the Davis Cup this year, in my book, are the Argentines, who take on a weakened Russian team at home.

The Argentine team has flaws. In singles, David Nalbandian continues to fade after resurrecting his career last fall. Juan Martin del Potro, the 6-foot-5-inch 19-year-old who reached the U.S. Open quarterfinals and cleaned up during the summer hard court season, has played a lot of tennis this year and is relatively untested in the Davis Cup. The Argentines don’t field a consistent doubles team, either.

Why pick this team to win? Because it plays superb tennis at home. The Argentines haven’t lost a match at home since 1998, a streak of 12 victories. It should extend that streak against Russia, which is led by Nikolay Davydenko and does not have Marat Safin or Mikhail Youzhny, two superb Davis Cup players, at its disposal. If Argentina plays Spain in the final, it will have an excellent chance on a hard court, thanks to Nalbandian’s versatility and del Potro’s improved play. If the Americans happen to pull off an upset this weekend, they would be heavy underdogs against Argentina on clay.

Argentina has competed in the Davis Cup since 1923 and reached the finals twice, yet never won the title. It is the most talented tennis nation to never win — a reputation that could be rehabilitated by December.

Mr. Perrotta is a senior editor at Tennis magazine. He can be reached at tperrotta@ tennismagazine.com.