Paris - What looked like being a fairly straightforward assignment in Kazakhstan for Davis Cup holders the Czech Republic has turned into a quarter-final minefield following the late withdrawal of top player Tomas Berdych.
The towering Berdych, who led the Czechs to glory in the team competition last year against Spain, pulled out after injuring a shoulder in a quarter-final loss to Richard Gasquet in Miami last week.
That leaves Radek Stepanek, himself just back from neck surgery, as the Czech spearhead, but he will play only in the doubles alongside Ivo Minar with Lukas Rosol, and Jan Hajek taking the singles slots.
The Kazakhs will look to their number one Mikhail Kukushkin to provide the inspiration in Astana backed by Andrey Golubev, who has a fine Davis Cup record on home soil.
The only previous time the two teams met in the competition was in 2011 when Kazakhstan won in the first round.
The Kazakhstan v Czech Republic tie is the only one of the weekend's quarter-finals to be played in Europe - with the others being held in the United States, Canada and Argentina.
In Boise, Idaho, world number one Novak Djokovic continues his love affair with the Davis Cup as he once again leads Serbia into battle against the United States.
Djokovic was the inspiration behind the Serbs first ever Davis Cup crown win in 2010, and he was the first name on captain Bogdan Obradovic's list for the trip to the United States.
Viktor Troicki will get the second singles slot and he will most likely link up with the hugely experienced Nenad Zimonjic for Saturday's doubles tie going up against the mighty Bryan twins, Bob and Mike, who are 20-3 in Davis Cup play and won Olympic gold in London last year.
US skipper Jim Courier will field the giant pair of John Isner and Sam Querrey in the singles, with the latter having just taken over the US number one spot last week at 20th in the world.
The Americans, who defeated Brazil in the first round, lost their only prior Davis Cup meeting with Serbia 3-2 in the opening round at Belgrade in 2010, when Djokovic led Serbia to the title.
"It's going to be very exciting," said Isner. "(Playing Serbia) is going to be a huge challenge. The guy that anchors their team is the best player in the world so we're certainly going to have our hands full but it's going to be a lot of fun."
Vancouver's Thunderbird Sports centre has been chosen to stage the Canada v Italy matchup with the playing surface seen to be particularly suitable for Canadian number one Milos Raonic.
The stakes will be high as between them the two countries have just the one Davis Cup triumph - going to Italy in 1976.
Raonic will be key to Canadian hopes of a first ever World Group semi-final and will likely have to win both of his rubbers against world No 19 Andreas Seppi and world No 36 Fabio Fognini.
"Playing in the Doug Mitchell Thunderbird Arena last time showed that the fans in Vancouver are really strong and I'm happy to be back in that atmosphere," said Raonic.
"It's going to be exciting to play a strong Italian team. They're going to be bringing a very strong team with them this year with (Andreas) Seppi in good form and Fabio (Fognini) who is capable of some good wins."
The prize for the winner of this tie will be a clash with the winner of the United States versus Serbia tie.
The remaining quarter-final takes place on the claycourts of Buenos Aires with what looks like an evenly-balanced match opposing Argentina and France.
France have impressive strength in depth but were hit by the late withdrawal of world top tenner Richard Gasquet due to an infected blister on his foot.
Still, they can call on their No 1 player Jo-Wilfried Tsonga and with world No 13 Gilles Simon taking the second singles berth.
Michael Llodra and Julien Benneteau form a formidable doubles pairing which will confirm the French as favourites.
But the slow clay surface will benefit the South Americans and boost their hopes even if they will have to do without top player Juan Martin del Potro, who is unavailable.
The Argentinians will field Juan Monaco, the veteran David Nalbandian as well as Carlos Berlocq and Horacio Zeballos, all of whom are at home on the clay.
"It is 50-50. Historically, playing over there is not easy," said new French captain Arnaud Clement.
"I think Argentina will be strong and be up for it. They have won 18 of their last 20 home matches."