Davis Cup giants Australia, US, Russia and France faced tension-packed matches yesterday as they battled to book quarter-final places in this season's competition.
For the first time in the 27 years of the World Group, all eight first round ties were still live going into the final day.
Lleyton Hewitt teamed-up with Paul Hanley in doubles as Australia, the 28-time champions, kept their tie in Belgium alive after losing both singles on Friday.
Hewitt and Hanley produced a 6-2, 6-4, 6-2 win over Kristof Vliegen and Olivier Rochus.
Saturday's win still left Australia with a huge ask in yesterday's reverse singles, with Hewitt up against Rochus in the fourth rubber and Chris Guccione set to face Vliegen in the potentially deciding fifth.
"It's going be a tough match," Hewitt said. "I'll try to get off to a good start and put some early pressure on him. I'm going to be better for having played on Friday, getting a feel for the court and the atmosphere."
In Ostrava, Mike and Bob Bryan confirmed their status as the world's top doubles pair by giving the US a 2-1 lead over the Czech Republic.
The Bryans cruised to a 6-4, 6-4, 6-4 win over Lukas Dlouhy and 36-year-old doubles veteran, Pavel Vizner, to leave the US needing just one reverse singles win yesterday to claim a quarter-final place.
Defending champions Russia lost Saturday's doubles to Chile at La Serena to also stand 2-1 ahead.
Olympic gold medalists Fernando Gonzalez and Nicolas Massu kept Chile's hopes alive by securing a 7-6 (7/3), 6-3, 6-4 win over Igor Andreev and Marat Safin, the Russian duo who had won Friday's singles.
Russian captain Shamil Tarpischev had gambled by employing Safin and Andreev instead of Teimuraz Gabashvili and Igor Kunitsyn, but the plan backfired.
Nine-time champions France squandered their chance to wrap up their tie with Romania after Florin Mergea and Horia Tecau won an epic doubles rubber against Arnaud Clement and Michael Llodra 3-6, 7-5, 7-5, 6-7 (3/7), 11-9 in four hours and 35 minutes.
In Geneva, another marathon doubles encounter kept Spain, without the injured Rafael Nadal, on course for the last eight after Feliciano Lopez and Fernando Verdasco took almost five hours to beat Switzerland's Yves Allegro and Marco Chiudinelli 7-6 (7/5), 6-7 (3/7), 6-7 (2/7), 6-1, 12-10.
In the remaining first round ties, Alexander Waske and Michael Kohlmann beat Mario Ancic and Ivan Ljubicic 6-4, 6-2, 7-6 (7/5) to give Germany a 2-1 lead over Croatia.
In Minsk, Belarus stayed alive against Sweden but trail 2-1 after Max Mirnyi and Vladimir Voltchkov beat Jonas Bjorkman and Simon Aspelin 7-5, 4-6, 7-5, 6-3.
Austria also won their crucial doubles against last year's runners-up Argentina in Linz to trail 2-1.
Jurgen Melzer and Julian Knowle saw off Sebastian Prieto and Jose Acasuso 6-3, 6-7 (2/7), 6-1, 7-5.