PARIS, Oct. 29 (Xinhua) -- American Andy Roddick and Argentine Juan Martin Del Potro boosted their chances of qualifying for next month's Masters Cup in Shanghai by winning their second-round matches at the Paris Masters on Tuesday.
Serb's third seed Novak Djokovic was leading 6-2, 4-3 against Dmitry Tursunov when the Russian retired with an injured right shoulder while seventh-seeded Roddick beat Feliciano Lopez of Spain 6-3, 6-4.
The rising star Del Potro, winner of four titles this season, swept past Croat Mario Ancic 6-0, 6-4 to reach the last 16.
Del Potro, on course for a quarterfinal against Murray, said he had to admit Shanghai was on his mind - as well as a Davis Cup final against Nadal's Spaniards.
Three spots for next month's Masters Cup are still up for grabs in Paris with Roddick, Del Potro and France's Gilles Simon, eighth in the ATP Race, occupying the remaining places at the start of the tournament.
Elsewhere, 15th-seeded Fernando Verdasco outlasted Spanish countryman Tommy Robredo 6-2, 6-7(6), 6-2, and 16th-seeded Gael Monfils topped Juan Monaco of Argentina 6-4, 6-4 to set up a possible match against top-ranked Rafael Nadal.
In first-round action, new Lyon Grand Prix champion Robin Soderling won his sixth straight match against Josselin Ouanna of France 6-3, 6-4 to set up an eighth career meeting with Roger Federer.
Soderling was 0-7 against Federer, who won his 57th career title at the Swiss Indoors on Sunday.