Serbia moved to the brink of a famous Davis Cup victory over USA as Victor Troicki and Novak Djokovic posted singles wins on day one of their World Group tie.
Troicki toppled 6ft 9in world No.20 John Isner 7-6 (7-4) 6-7 (5-7) 7-5 6-4 in the opening rubber before Djokovic recorded a more expected win over Sam Querrey to give the hosts a 2-0 lead in Belgrade.
The world No.2 was given a battle, though, before eventually prevailing 6-2 7-6 (7-4) 2-6 6-3.
USA are now relying on top doubles team Bob and Mike Bryan winning tomorrow's rubber to keep the tie alive.
David Ferrer drew reigning champions Spain level at 1-1 with Switzerland by beating Marco Chiudinelli 6-2 7-6 (7-5) 6-1.
In the first rubber, Stanislas Wawrinka had put the visitors ahead with a hard-fought 3-6 6-4 3-6 7-5 6-3 victory over Nicolas Almagro in Logrono.
It was an impressive effort from Wawrinka, who had not played a competitive match in six weeks following the birth of his daughter Alexia.
Gloss was taken off the tie somewhat when it was confirmed it would not feature a clash between the two most successful players of the current era, Switzerland's Roger Federer and Rafael Nadal of Spain.
Gael Monfils secured his first ever Davis Cup victory, a convincing 6-1 6-4 7-6 (7-5) win over Philipp Kohlschreiber, as France moved into a 2-0 lead over Germany in Toulon.
Monfils told www.daviscup.org: "It was one of my best matches of the season. I'm very happy with the way I moved on the court and the way I controlled the match, and of course very happy to bring the point for France."
Jo-Wilfried Tsonga built on his team-mate's landmark win with a 6-3 6-2 6-7 (2-7) 6-3 victory over Benjamin Becker.
The Czech Republic and Croatia also moved to the brink of victory on day one after taking 2-0 leads against Belgium and Ecuador respectively.
The Czechs breezed through proceedings, with Tomas Berdych beating Olivier Rochus 6-3 6-0 6-4 and Radek Stepanek defeating Xavier Malisse 6-2 6-4 7-6 (7-3).
Things were somewhat different for giant Croatian Ivo Karlovic, who needed three hours and 45 minutes to beat Nicolas Lapentti.
In a match that ebbed and flowed, the big-serving Croatian prevailed 6-2 5-7 6-7 (2-7) 6-3 6-4 to put his country 1-0 up in Varazdin.
"I started well but he came back strongly to win the next two sets and I was really happy to claw victory from the jaws of defeat after coming from behind," said Karlovic.
"My serve is my most powerful weapon and it didn't let me down but I knew this was never going to be an easy match."
Marin Cilic was more convincing against the other Lapentti brother, Giovanni, coming through 6-4 6-3 6-3.
Sweden and Argentina are level at 1-1 in a tie notable for the return of Joachim Johansson.
The former world No.9 retired in February 2008 because of a persistent shoulder injury before changing his mind nine months later.
He played mostly in Challenger events last year and is competing in his first Davis Cup tie since 2007 this weekend.
However, there was to be no fairytale for Johansson, now ranked 373rd, as he went down 5-7 6-3 7-5 6-4 to Leonardo Mayer, after Robin Soderling had beaten Eduardo Schwank 6-1 7-6 (7-0) 7-5 in the opening rubber.
Russia is closing in on victory against India in Moscow, establishing a 2-0 lead after the first day's singles matches.
First Igor Kunitsyn came from a set down to beat Somdev Devvarman 6-7 (6-8) 7-6 (7-4) 6-3 6-4 then Mikhail Youzhny showed his class in a 6-4 6-2 6-3 demolition of Rohan Bopanna.