The Swiss ace looked on course for the third round after cruising through the first set but came unstuck in the second as uncharacteristic errors began to creep into his game.

Benneteau, the world number 49, was roared on by his home crowd and secured the result of his life with an ace after bringing up match point by rattling a crosscourt backhand past the 15-time Grand Slam-winner.

"He was very strong at the end," said Federer of his 27-year-old opponent, who has never won an ATP title.

"Even in the second set, I don't think I had a break point.

"I can definitely play better but I can also play much worse. It wasn't a bad performance. Julien went out and got the victory. I had chances and missed them."

Second seed Rafael Nadal, meanwhile, admitted that he was "very lucky" after edging a titanic struggle with Spanish compatriot Nicolas Almagro 3-6, 7-6 (7/2), 7-5 in three hours and 14 minutes.

"I played great tennis in only one moment, but in the rest of the match I didn't play well," said Nadal, who saved five match points after falling 5-6 and 0-40 down in the second set.

"I am very lucky to be in the (next) round. That's the truth. I played bad but I won, which is the one positive thing."

Nadal will now face another Spaniard in the form of 14th seed Tommy Robredo.

The world's top five players were all in action on Wednesday, with Novak Djokovic, Andy Murray and Juan Martin Del Petro all joining Nadal in the third round.

British fourth seed Murray saw off America's James Blake 6-3, 6-7 (5/7), 7-6 (7/4) in a match that finished at 0146 local time to set up a match with Czech 13th seed Radek Stepanek.

Marat Safin's 6-4, 5-7, 6-4 defeat to fifth seed Del Potro heralded the end of the Russian former world number one's career, after he announced earlier in the year that he would retire at the end of the season.

"This day will stand out for a long time, until I pass into a different world," Safin, a three-time winner here, told the crowd at the Bercy arena during a special post-match ceremony.

"This day will be where all the memories of my career will stay, all in one box."

Third seed Djokovic, who beat Federer in the Basel final on Sunday, overcame Argentina's Juan Monaco 6-3, 7-5.

"I didn't feel that great on the court," said Djokovic.

"It was probably a long week in Basel that affected that. But I got a victory and that's what matters most. Generally speaking I've picked up great form in the last two months."

Djokovic will now face French qualifier Arnaud Clement, a 5-7, 6-3, 7-6 (10/8) winner over German 16th seed Tommy Haas, with Del Potro to play Chilean 10th seed Fernando Gonzalez.

Swedish ninth seed Robin Soderling kept alive his hopes of snatching a place at the ATP World Tour Finals in London by defeating Croatia's Ivo Karlovic 6-4, 7-6 (8/6).

Soderling is one place outside the eight qualifying berths for the year-end event but needs to at least reach the final here to stand any chance of securing one of the last two available spots and will meet Russian Nikolay Davydenko, currently seventh in the race to London, in the next round.

Benneteau's next opponent will be countryman Gael Monfils, the 15th seed, who beat David Guez 6-4, 7-5, while Croatian 12th seed Marin Cilic faces Spain's Fernando Verdasco after coming from behind to beat Polish qualifier Lukasz Kubot 6-7 (3/7), 6-4, 6-2.