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.
The Serb, newly dethroned from the number one ranking by Rafael Nadal, played down the incident afterwards.
"It was just an awkward movement. I was in an off-balance position. I was running and I made a quick movement that caused a sharp pain at that instant moment," he said.
"But after the match we determined that it's nothing serious, so it's all fine," he added.
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 number 22, repeating the feat to take the opening set. A single break in the second was enough to seal the match.


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