Holders Spain face a fight for life without Rafael Nadal after France took a 2-0 lead in their Davis Cup World Group quarterfinal tie.
The hosts now stand one win away from a historic first after last beating their southern neighbours in 1923 in the worldwide team competition.
Frenchman Gael Monfils, leading the effort on Friday in the injury absence of Jo-Wilfried Tsonga, started the weekend in five sets to stun David Ferrer 7-6 (7-3), 6-2, 4-6, 5-7, 6-4, the Spaniard's first loss in the competition after eight consecutive wins.
Michael Llodra placed France in an enviable position through his subsequent upset of Fernando Verdasco 6-7 (5-7), 6-4, 6-3, 7-6 (7-2).
The French are seeking a first semifinal since 2004.
Nadal, who won his second Wimbledon title at the weekend, said he would not play Davis Cup to seek treatment on his dodgy knee but is now flying to South Africa for the country's World Cup football final on Sunday against the Netherlands.
The Czech Republic also stand in the driving seat 2-0 over Chile after day one play.
In Moscow, Argentine David Nalbandian made a successful comeback to tennis after three months away as he beat Russian Nikolay Davydenko 6-4, 7-6 (7-5), 7-6 (8-6) to give his nation a 1-0 lead.
That tie is level at one apiece after Mikhail Youzhny squared for this hosts over Leonardo Mayer 6-3, 6-1, 6-4.
In Coquimbo, Chile, the visiting Czechs took control of that tie through wins from Ivo Minar, 6-0, 6-2, 6-3 over Nicolas Massu, and a victory by substitute Jan Hayek over Paul Capdeville 6-0, 6-2, 6-1.
Czech Wimbledon finalist Tomas Beredych is skipping the weekend through injury and fatigue.
World number two Novak Djokovic kept Serbia in the chase in Split as the visitors stand knotted 1-1 with Croatia.
Djokovic beat veteran campaigner Ivan Ljubicic 7-6 (7-3), 6-4, 6-1, but Croatia's Marin Cilic pulled the hosts back at one each as he beat Viktor Troicki 6-4, 7-5, 6-2.
"I started this season real well, reaching the Top-10 ranking, which was my goal," said Cilic. "But as the season progressed, I lost my form.
"Playing in the Davis Cup lifts my self-confidence, like it did last year when we had a great run to the semi-finals."
Ljubicic was playing for the first time in three-and-a-half years after coming out of Davis retirement to help his injury-hit side.
In Moscow, Mikhail Youzhny brought Russia back to 1-1 against Argentina in a replay of the 2006 final won by the Russian. Earlier, Argentine David Nalbandian made a successful comeback to tennis after three months away as he beat Nikolay Davydenko 6-4, 7-6 (7-5), 7-6 (8-6)
Nalbandian underwent hip surgery in spring 2009, but then had to face hamstring and abdominal muscle problems. He last played on the ATP in April at Monte Carlo.
"I didn't play my best tennis," said the winner. "It's difficult coming back from injuries and returning at the Davis Cup.
"I played the important points better and took advantage of my chances. I was a bit better on the day."
The 28-year-old is due for service all three days of the tie for Argentina, continuing with Saturday doubles.