US star Andy Roddick reached the quarter-finals of the Paris Masters on Thursday and in so doing clinched his season-ending Shanghai Masters Cup berth, beating Gilles Simon of France 6-3, 7-5.
Simon stood eighth in the ATP Race going into Thursday's match but realistically needed to win as James Blake of the United States and Jo-Wilfried Tsonga are breathing down his neck.
For Roddick, his win cemented sixth spot and he next faces either Tsonga or third seed Novak Djokovic, who were facing off in a repeat of the Australian Open final won by the Serbian.
Argentine eighth seed and title-holder David Nalbandian earlier thrashed his ninth-seeded Davis Cup teammate Juan Martin Del Potro 6-4, 6-0 to become the first quarter-finalist at the Paris Masters.
Nalbandian, who took the pair's series to 3-1 in his favour in their third meeting inside a month, next faces either fourth-seeded Briton Andy Murray or Spanish 15th seed Fernando Verdasco.
A missed break point - one of four in total - in the seventh game of the second set was the closest Simon came to an upset. In a high-wire act he saved four match points in the 12th game before succumbing.
With his loss to Nalbandian, Del Potro, suffering from a broken toenail, now must sweat on joining Roddick in China.
The rising star is seventh in the ATP Race but could slide out of the eight-man field depending on other results here.
"I don't like playing against friends or Argentinian players - it's tough," said a crestfallen Del Potro.
"David did a great match. I don't know if I'll play Shanghai - I'm not qualified yet.
"At least if I don't I have the Davis Cup for sure - and that gives me plenty of motivation."
Nalbandian, who assured Spanish reporters the Argentine crowd would give them a warm Davis Cup welcome in Mar del Plata, said Murray would be a huge obstacle.
"He's doing great - won a lot of important titles. He's a talent."
Murray is seeking this week to become the first man to win three straight Masters events after triumphs in Cincinnati and Madrid.
Nalbandian could still theoretically qualify for China - "I will see if and when the time comes," he insisted - but is focused on teaming up with Del Potro afterwards as Argentina target a first Davis Cup final at the expense of Rafael Nadal's Spain on November 21-23 in Mar del Plata.
After Roddick's win, two Shanghai slots remained up for grabs on a day when nine of the world's top ten were in action.
In evening play, world number one Nadal was taking on French hope Gael Monfils while second-ranked Roger Federer was meeting Croatian Marin Cilic.
Sixth-seed Nikolay Davydenko of Russia was playing Tomas Berdych in the late match in a battle of former champions.