Novak Djokovic's two recent defeats after a 22-match winning streak offer the United States hope of seeing off Serbia in the Davis Cup quarter-finals starting on Friday.
The mere presence of the top-ranked Djokovic make Serbia slight favourites, but the Americans chose to play on an indoor hard-court at altitude in Boise, Idaho, to give their big servers a boost.
It's a bonus to the U.S. that Djokovic has appeared vulnerable in the past month, with two defeats in his last four matches.
However, he appears to have brushed them off this week, saying, "I always love these seven to 10 days spending with friends just representing Serbia, it's really fantastic."
In the other quarter-finals, Argentina host France, Kazakhstan welcome the defending champions Czech Republic, and Canada face Italy.
Djokovic recommitted to Davis Cup after skipping last year's campaign, and helped Serbia cruise past Belgium in February.
He beat Sam Querrey and John Isner in the only previous Serbia-U.S. tie, during the 2010 title run, and Serbia are likely to need a point from Viktor Troicki or the doubles to advance.
The doubles had been a reliable point for the U.S. until the Bryan brothers suffered a rare cup loss in the struggle to get past Brazil at home in the first round.
Berdych Czech's out
The Parque Roca in Buenos Aires will need to be a fortress again if Argentina are to beat France for the first time.
Argentina have lost all five previous ties with France, including being beaten 5-0 in the 2010 semi-finals in Lyon.
Without Juan Martin del Potro again, the same team which beat Germany 5-0 will line up on clay against the same France team which defeated Israel by the same score. Top-10 players Jo-Wilfried Tsonga and Richard Gasquet are complemented by accomplished doubles pair Julien Benneteau and Michael Llodra.
The Czech Republic risk becoming the third defending champions in seven years to fall in the quarters.
"We're going to go in with the same mentality and if we put up the same performance I think we'll have a good chance to win"
Canada's Vasek Pospisil
In the absence of his longtime partner Tomas Berdych, Radek Stepanek will spearhead the Czechs against hosts Kazakhstan. Stepanek hasn't played since an early defeat in the Australian Open, after which he underwent surgery on a disc in his neck.
While he was sidelined, the sixth-ranked Berdych won all three points against Switzerland. But after reaching two ATP finals, a semifinal and quarter-final, he injured a shoulder and will miss his first tie in three years.
Fortunately for the Czechs, Stepanek is now available, but he will play his first tie without Berdych since his cup debut 10 years ago.
Their reliance on Stepanek and Berdych, who won all 12 live points last year for the Czechs' first cup in 32 years, is reflected in the lack of cup experience of their teammates. Lukas Rosol, who paired with Berdych to win the longest match in cup history against the Swiss, a seven-hour doubles contest, will play his fifth tie in two years. Jan Hajek has not featured in the cup since 2011, and Ivo Minar has four ties in six years.
None of Kazakhstan's main players - Evgeny Korolev, Andrey Golubev and Mikhail Kukushkin - has won a main draw match on the ATP Tour since at least August, but they were still too good for Austria in February. They also have history on their side; they upset the Czechs two years ago.
Canada carries the confidence of beating mighty Spain in February to reach their first cup quarter-final in the same indoor Vancouver venue.
"We're going to go in with the same mentality and if we put up the same performance I think we'll have a good chance to win," Canada's Vasek Pospisil said of meeting Italy.
Italy have a shot at their first semifinals since 1998, with only a doubt over Simone Bolelli, half of the world No. 3-ranked pairing with Fabio Fognini. Bolelli has an injured wrist.