David Nalbandian enhanced his reputation as Roger Federer's [Images] nightmare opponent by upsetting the world number one again with a 6-4, 7-6 win in the Paris Masters Series third round on Thursday.

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Eleven days after beating Federer in the Madrid Masters final, the unseeded Argentine showed more composure when it mattered to oust the elegant Swiss, who had already made sure of ending the season in top spot for a fourth consecutive year.

"Of course, it's disappointing to lose to a guy two times in a couple of weeks, especially indoors, one my favourite surfaces, but we knew the qualities of David," Federer told reporters.

"I wish conditions were a bit faster because indoors is supposed to be fast," he said. "Not here, I guess."

Nalbandian, now tied at 8-8 with an opponent he famously defeated in the 2005 Masters Cup final, goes on to meet Spain's David Ferrer for a place in the semi-finals.

Ferrer, seeded fifth in the $2.45 million indoor event, advanced to the last eight by knocking out Czech Tomas Berdych, the 2005 Paris champion, 6-4, 6-2.

Nalbandian took a perfect start, opening up a 5-2 lead. Federer fought bravely and had saved five set points when Nalbandian eventually took the set with a superb cross-court forehand winner.

The Argentine stayed on top in the second set and served for the match, leading 5-4, but Federer managed to break him and force a tiebreak, in which he survived a match point before hitting a forehand long to enable his opponent to win it 7-3.

MURRAY CLOSER

British number one Andy Murray had earlier moved closer to a Masters Cup spot by crushing Frenchman Fabrice Santoro 6-4, 6-2 to reach the quarter-finals.

The 20-year-old Murray, one of several players fighting for the two remaining tickets to the November 11-18 season-finale in Shanghai featuring the world's top eight, needed just 69 minutes to brush aside the 34-year-old.

The Scot could score points in the next round when he faces another Masters Cup contender in Frenchman Richard Gasquet, who pleased the home crowd with a 6-4 6-4 win over American James Blake.

World number two Rafael Nadal [Images], playing the tournament for the first time, advanced in determined fashion with a 6-4 6-3 win over Swiss Stanislas Wawrinka.

The Spaniard next meets Russia's [Images] Mikhail Youzhny, who ended German Tommy Haas's Masters Cup hopes by beating the German 6-4, 1-6, 6-3 in Thursday's last match.

The day had started with Cypriot Marcos Baghdatis knocking out title holder Nikolay Davydenko with an impressive 6-2, 6-2 win to keep alive his own Masters Cup hopes.

Baghdatis gave a near faultless display to set up a quarter-final with Spain's Tommy Robredo, the eighth seed, who overcame Argentine Guillermo Canas 7-5, 7-5.

Russia's Davydenko, seeded fourth, looked sluggish before bowing out with a backhand error at the end of a one-sided contest lasting just 73 minutes.

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