Stanislas Wawrinka survived a second-set wobble to beat Jo-Wilfried Tsonga 6-1, 3-6, 6-3, 6-2 and give Switzerland a 1-0 lead over hosts France in the Davis Cup final on Friday.
World number four Wawrinka was more consistent than French number one Tsonga in front of a record 27,432 crowd at the Pierre Mauroy stadium.
In the second match, Gael Monfils rose to the occasion as he upset Roger Federer 6-1, 6-4, 6-3 to help France level.
Federer missed training this week after being forced to withdraw from his ATP World Tour Final against Novak Djokovic in London on Sunday.
Monfils, who had never beaten Federer on clay in four previous encounters, won five games in a row as he whizzed through the first set.
Struggling with his serve, the Swiss was broken again in the third game of the second set and his French rival showed no sign of weakening, sending his opponent chasing balls left, right and centre.
It was not game over yet, though, as Federer beat Monfils in five sets in this year's U.S. Open quarter-finals after dropping the first two.
But this time, roared on by a record 27,432 crowd that were kept quiet during Tsonga's match, Monfils maintained his grip to break for a 3-2 lead before finishing off the contest on Federer's serve with a stunning backhand winner down the line.
Earlier, Wawrinka breezed through the opening set, relying on his accurate one-handed backhand to unsettle Tsonga, who had trouble finding his range with his usually booming forehand.
The Swiss bagged eight points on his way to a double break, sealing the set when Tsonga sent a forehand long.
The Frenchman faced a break point in the opening game of the second set but saved it with a smash. Wawrinka then lost his sharpness and served a double fault to hand his opponent a 3-1 lead.
Tsonga held serve throughout and clinched the set with a service winner.
But he lost the momentum, conceding a break for 4-2 by spraying another forehand wide and Wawrinka sealed the set on his second opportunity with a crosscourt backhand winner.
Wawrinka piled on the pressure and a backhand volley earned him a break in the first game of the fourth set, which he firmed up with another break for 5-2 with a backhand winner.
The Australian Open champion, who hit 61 winners to Tsonga's 39, wrapped it up on his first match point with a routine volley following yet another charge to the net.
The doubles will be played on Saturday and the reverse singles on Sunday.
France, who last triumphed in 2001, are looking to win the Davis Cup for the 10th time while Switzerland are seeking their maiden title.
Image: Stanislas Wawrinka of Switzerland celebrates during his match against Jo-Wilfried Tsonga of France in the Davis Cup final in Lille.
Photo: Julian Finney/Getty Images
