With Federer a shock loser to Frenchman Julien Benneteau on Wednesday, a win for Nadal in Sunday's final would leave him just 305 points adrift of his arch rival with the season-ending ATP World Tour Finals to come in London later this month.

Nadal ended Federer's long reign as world No.1 after winning the Beijing Olympics last year, but Federer bounced back to regain the top spot in July after winning both the French Open and Wimbledon titles.

Nadal had needed to save five match points to get past Spanish compatriot Nicolas Almagro in a second round marathon of over three hours on Wednesday, and he wobbled again against Robredo, another countryman and a player he had beaten in straight sets in all five of their previous encounters.

Robredo even served for the match at 5-4 in the deciding set but once again Nadal produced his best with his back to the wall to pull through by winning the final three games of the match.

"I was a little less lucky than yesterday," Nadal said. "He served for the match and it was in his hands, but I won anyway.

"I wasn't playing my best, but I played better than yesterday."

Joining Federer on the sidelines though was fourth seed Andy Murray who found two matches in one day too much to handle as he lost 1-6, 6-3, 6-4 to Radek Stepanek of the Czech Republic.

The Scot, who won a season-best sixth title in Valencia on Sunday was taken to 1:45 a.m. the night before in defeating James Blake 6-3, 6-7 (5/7), 7-6 (7/4).

"I said last night it was going to be difficult to come back and feel 100 percent. It's obviously limited recovery after a long match," he said.

"But you still come out and you try to give it your best shot. Wasn't good enough."

Nikolay Davydenko meanwhile became the seventh player to qualify for the eight-man London Tour Finals despite losing 6-3, 3-6, 6-4 to Sweden's Robin Soderling in another third round match.

Placed seventh in the standings coming into Paris, the loss briefly left the Russian at the mercy of the four other players in with a chance of playing in London from Nov. 22-29.

But then Spain's Fernando Verdasco, who was holding on to the eighth and final slot, lost 3-6, 6-3, 6-4 to Marin Cilic of Croatia.

His defeat meant that Davydenko was assured of finishing the week no lower than eighth which stamped his ticket for London.

Verdasco was left having to sweat it out while keeping an eye on the progress of the three other potential finalists - Soderling, Jo-Wilfried Tsonga, who reached the last eight here with a 6-2, 6-3 win over French compatriot Gilles Simon, and Chile's Fernando Gonzalez.

Gonzalez though saw his hopes dashed in the final match of the day when he let slip seven match points in the second set to US Open champion Juan Martin del Potro of Argentina before abandoning at one set all 6-7 (6/8), 7-6 (8/6).

Soderling, who reached the French Open final the last time he was in Paris in June, will still have to at least reach the final at Bercy to have any chance of making it through to London.

Next up for him, with a place in the semi-finals at stake, will be third seed Novak Djokovic, who cruised past French qualifier Arnaud Clement 6-2, 6-2 in 75 minutes.

The 2008 Australian Open champion from Serbia, last year's Tour Finals winner, is seeking to lift back-to-back titles following his win in Basel last week where he beat Roger Federer in the final.

He is also eager to win his first Masters Series title of the year having lost in four finals.

"Robin has a chance to qualify for the Masters Cup so he will give his best in the quarter-finals," Djokovic said.

"He is a big server and is having the best year of his career. I played him recently in Beijing and won so, hopefully, I can do the same here."

Title-holder Tsonga, who needs to defend his title to qualify for London, said after his win over Simon that he refused to let himself become obsessed with qualifying for the season's finale.

"I'm not here for the Masters. I'm here for Bercy," the French No.1 said.

"I will only be qualified if I win this tournament, so I'm not thinking about London.

Benneteau, who said his win over the world No.1 Federer was the best moment of his career, failed to carry his form into Thursday losing 6-4, 6-3 to compatriot Gael Monfils.