Roger Federer says physical fitness will determine his schedule for the rest of the season, which begins with next week's Shanghai Masters.
"The next [few] weeks are extremely important, with Shanghai and Basel, maybe Paris, and the ATP Finals in London," Federer said, adding that his hometown tournament at Basel would "take priority" against the following week's Paris Masters, if he decides he cannot play both events.
Federer said that he is not as concerned with No. 1 because of Nadal's almost 2,000-point lead in the rankings. "I will concentrate on myself, and play just when I am ready," he said.
Federer has won five of the nine events he has played this season, and is currently No. 2 in the rankings.
