Rafa Nadal, who just withdrew from Basel due to a knee injury, says Roger Federer has played at a very high level this season while also taking time off to recover.

Federer has beaten the No. 1-ranked Nadal all four times they have played this season—all on hard courts. Both have won half a dozen titles, but Federer has played fewer events.

“He's winning two Grand Slams, winning couple of Masters 1000s, being second on the race with a lot of points. Yeah, played well, for the whole season,” Nadal said following his defeat in the final of Shanghai. “And the good thing for him is he take the periods of rest and when he was back he was able to win. So that makes a difference, because is very easy to say, okay, I take this period of time and that works very well. That works very good if you come back, win. Because if you come back, you don't win, then for sure is not working well.”

The 36-year-old Federer skipped the clay season, while Nadal played a ton of matches on the surface, winning the French Open and three other clay tournaments.

Nadal also played consecutive weeks to win Beijing and reach the final in Shanghai, though he looked a little bit tired and was wearing tape on his knee in the final against Federer.

But the Spaniard says players can't just take extended breaks as successfully as Federer has this season.

"The calendars are always looking good or looking bad in terms of the results. When somebody is winning a lot, looks like calendar is perfect," said Nadal. "When somebody is losing, looks like the calendar is not good. For this year, Roger did great in all the events that he played, so looks like he saved his body, he did the right things, but at the same time anything could happen. And the confidence is going up and down sometimes. You can lose a couple of matches and changes everything, but of course he did unbelievable. He played very high level of tennis during the whole season."