Argentina's Juan Martin del Potro overcame a second-set lapse and a left wrist injury to defeat Serbia's Viktor Troicki 7-6 (7-2), 2-6, 6-1 Thursday and advance to the quarterfinals of the Western and Southern Open in Cincinnati.

The match became complicated for the Argentine when he began experiencing pain in the left wrist in the second game and had to call for the trainer.

The ninth-ranked Del Potro, who missed nearly the entire 2010 season with a right wrist injury, decided to continue after receiving medical assistance but the ailment limited his use of the two-handed backhand, one of his most solid strokes.

Forced to hit mostly slice backhands and frequently cede the initiative in the rallies against his 32-ranked opponent, the bronze medalist at the London Olympics needed two hours and 16 minutes to come away with the victory.

In another match Thursday, Spain's last remaining player in the tournament, Pablo Andujar, lost to Croatia's Marin Cilic 7-6 (7-4), 6-2.

The Iberian nation's top player, world No. 3 Rafael Nadal, pulled out of the tournament due to a nagging knee injury and also has withdrawn from the U.S. Open, the year's last Grand Slam event.

Among the top seeds in Cincinnati, world No. 1 Roger Federer of Switzerland cruised into the quarterfinals with a 6-2, 6-4 victory over Australia's Bernard Tomic, but world No. 4 Andy Murray - the men's singles gold medalist in London - crashed out with a 6-4, 6-4 loss to France's Jeremy Chardy.

In Friday's quarterfinals, Federer will play American Mardy Fish, Switzerland's Stanislas Wawrinka will square off against either Canada's Milos Raonic or Czech Tomas Berdych, Del Potro will take on Chardy and Cilic will meet either world No. 2 Novak Djokovic or Russia's Nikolay Davydenko.

The Western and Southern Open is one of nine ATP World Tour Masters 1000 events and a key tune-up for the U.S. Open, which gets underway later this month. EFE