Defending champion Novak Djokovic shrugged off an injury scare to win his Shanghai Masters opener on Wednesday, keeping alive the prospect of a mouth-watering quarterfinal against Roger Federer.

In the late-evening match in second-round play, newly re-crowned world No. 1 Rafael Nadal polished off Ukraine’s Alexandr Dolgopolov in less than an hour, with just five unforced errors in a 6-3, 6-2 win.

Top seed Djokovic cantered through the first set against Spain’s Marcel Granollers for the loss of only two games. But early in the second he pulled up in obvious discomfort and called for the ATP trainer, who applied heavy taping to his right foot and ankle.

Despite the medical treatment, the 26-year-old did not look inconvenienced as he returned to the court to seal a 6-2, 6-0 victory, hitting a total of 26 winners.

Federer, who has slipped to seventh in the world rankings and faces a battle to qualify for next month’s World Tour Finals in London, won 6-4, 6-3 against Italian Andreas Seppi after a testing start.

The Swiss great, playing his first match since a disappointing US Open, lost his serve early but broke back immediately against the world No. 22, repeating the feat to take the opening set. A single break in the second was enough to seal the match.

Federer, who had a mixed bag of 19 winners and 29 unforced errors, said going a set up and then a break up in the second set was key for him and he started to feel comfortable.

del Potro survives

Earlier, German world No. 23 Philipp Kohlschreiber rattled a feverish Juan Martin del Potro, striking 50 winners and 22 aces in a brave display of attacking tennis that had the Argentine searching for answers before he dug deep to win 3-6, 6-3, 7-6(4).

“Last night I couldn’t sleep really well,” said the sixth seed, fresh from winning the Japan Open. “This morning I took ibuprofen, a couple of pills, trying to help me feeling better. But I’m not 100 per cent fit yet.”

“I think my serve helped me a lot to keep playing for the three sets because I made many aces,” added del Potro, who hit 14 aces.

Third seed David Ferrer beat Lukas Rosol 6-3, 6-4, fourth seed Tomas Berdych beat Feliciano Lopez 7-6(5), 6-2 and seventh seed Jo-Wilfried Tsonga eased past Pablo Andujar 6-3, 6-2.

There were also wins for seeds Tommy Haas, Stanislas Wawrinka and Kei Nishikori. But America's top player John Isner lost in straight sets to Argentina’s Carlos Berlocq.

Spain’s Tommy Robredo retired from his match against Italy’s Fabio Fognini.

Djokovic, Nadal and Ferrer have already qualified for the end-of-season showpiece in London. Britain’s Andy Murray has withdrawn from the tournament as he recovers from back surgery.

The wet weather relented on Wednesday.

The results: Second round: Milos Raonic bt Fernando Verdasco 7-6(1), 3-6, 6-3; David Ferrer bt Lukas Rosol 6-3, 6-4; Rafael Nadal bt Alexandr Dolgopolov 6-3, 6-2; Roger Federer bt Andreas Seppi 6-4, 6-3.

Stanislas Wawrinka bt Kevin Anderson 6-4, 3-6, 7-6(5); Nicolas Almagro bt Jeremy Chardy 6-3, 6-4; Kei Nishikori bt Jurgen Melzer 6-4, 3-6, 6-1; Gael Monfils bt Vasek Pospisil 7-5, 7-6(4); Florian Mayer bt Benoit Paire 7-6(1), 7-5; Novak Djokovic bt Marcel Granollers 6-2, 6-0; Tomas Berdych bt Feliciano Lopez 7-6(5), 6-2.

Tommy Haas bt Daniel Brands 6-4, 6-4; Juan Martin del Potro bt Philipp Kohlschreiber 3-6, 6-3, 7-6(4); Carlos Berlocq bt John Isner 6-4, 7-6(4); Jo-Wilfried Tsonga bt Pablo Andujar 6-3, 6-2; Fabio Fognini bt Tommy Robredo 7-6(3), 2-1 (retd.).

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