Rafael Nadal played down concerns about any knee problems after suffering a straight-sets defeat to Roger Federer in the Shanghai Masters final on Sunday.

For the first time this week, the world number one played with tape under his right knee, leading to questions over his fitness after a busy season.

But Nadal was quick to dismiss those queries, insisting he has no worries as the end-of-year ATP World Tour Finals approach.

"I don't want to talk about that [the knee] now, sorry, but after losing a final is not the moment," he said after the 6-4 6-3 loss.

"I am not worried though."

With the World Tour Finals taking place in London next month, it remains to be seen which, if any, tournaments Nadal will play beforehand, and he – like Federer - is not clear on the issue.

"I don't know [if I will play Basel or Paris]," he added. "I need to think about it. I cannot tell you [what the schedule will be]."

Sunday's final was decided by a break of Nadal's serve in each set, the elegant Federer working openings to pick up an impressive victory.

And his opponent – and recent doubles partner at the Laver Cup – was very impressed by his Swiss foe.

"It was a very difficult match for me," said Nadal. "He played very fast and he played well. 

"I don't know how many unforced errors he made. I could have done some things better, but that's it. He just played too good. That's my point of view. So congratulations to him."