Eight nations head to Malaga this week for the knockout stage of the 2023 Davis Cup Finals including Great Britain, who are chasing an 11th title at the 'World Cup of Tennis'.
The British team saw off Australia, Switzerland and France to seal progress from the group stage in September and have been rewarded with a quarter-final clash with 13/8 favourites Serbia.
The format, which has undergone several tweaks in recent years, remains the same as 2022, with the four quarter-finals taking place from Tuesday to Thursday.
Each quarter-final features two singles matches and, if the score is level after the singles, a deciding doubles rubber.
The winning teams progress to the semi-finals, which take place on Friday and Saturday, before the final on Sunday.
Defending champions Canada are out of the Davis Cup after being eliminated by underdogs Finland in a thrilling opening match to this year's tournament.
Backed by a raucous crowd of over 3,000, Finland had a fantastic following that cheered their heroes to the most unlikely of victories over the 8/1 champions.
The Fins did it the hard way after losing the first tie when Milos Raonic took a straight sets victory in the opening match, before Otto Virtanen battled back to beat Gabriel Diallo 6-4 7-5 to level the tie against the 2022 winners.
Virtanen and his doubles partner Harri Heliovaara then took the decisive doubles match 7-5 6-3 against Vasek Pospisil and Alexis Galarneau.
Finland's famous victory sees them set up a mouth watering tie against either Australia or Czechia in the semi-finals on Friday.
It is the first time they have ever reached the final four of the Davis Cup and they become the first Scandinavian nation to reach the that stage since Sweden way back in 2007.
Great Britain are 11/2 to win the Davis Cup, but Leon Smith's team will have to do it the hard way because Serbia, who they meet in Thursday's fourth quarter-final, are expected to have the mighty Novak Djokovic spearheading their bid for a second Davis Cup crown.
Djokovic has enjoyed a stellar year on an individual level, claiming three Grand Slam titles, and he would love to lead his country to Davis Cup glory again having done so in his nation's capital, Belgrade, in 2010.
The world no.1 will be the heavy favourite to defeat Cameron Norrie in the battle of the two highest-ranked players on each side but, the top two aside, there is not a great deal between the teams.
Smith has lost the services of Dan Evans and Andy Murray, who both withdrew with injuries, although that could prove a blessing in disguise because Evans' absence allows the British captain to add a second doubles specialist in Joe Salisbury.
Salisbury, ranked 12th in the world, can team up with world no.4 Neal Skupski, while Murray's decision not to participate also paves the way for the in-form Jack Draper to feature as the second singles player.
Draper, set to meet Laslo Djere in his singles rubber, won a Challenger Tour title in Bergamo at the beginning of November, before reaching the final of the Sofia Open, so this could well come down to the doubles.
The presence of Djokovic makes Serbia favourites, but another nation has a world-class star in their ranks and that's Italy, who include world no.4 Jannik Sinner as part of a strong squad which is 7/2 to win the Davis Cup for the first time since 1976.
However, with singles no.2 Lorenzo Musetti struggling, the importance of Sinner winning is massive for Italy.
They will hope Musetti can find his best form to avoid relying on a doubles victory over the strong Netherlands pairing of Wesley Koolhof and Jean-Julien Rojer.
Tallon Griekspoor and Botic van de Zandschulp are solid singles options for the Dutch, who could spring a surprise, particularly if Sinner is feeling weary after facing Djokovic at the ATP Finals on Sunday.
The winner of that quarter-final will face either Serbia or Great Britain in the semis, so there is a chance that a less fancied nation reaches the final from the weaker top half.
Of the four teams in the top half, Australia look to have the best chance of reaching the final and tee up a tilt at a 29th Davis Cup title, a record only bettered by the United States of America.
Lleyton Hewitt's team lacks stardust in singles, but Alex de Minaur is a steady operator with a 13-6 Davis Cup record, while Max Purcell has climbed into the world's top 50, having began the season outside the top 200.
Purcell, who is also likely to partner Matthew Ebden in doubles, will have a significant role to play for Australia, who begin their knockout stage campaign against a weak-looking Czechia team on Wednesday.