Twenty-time grand slam winner Rafael Nadal has refused to put a timeline on his comeback to competitive tennis and will only return when he is in "good condition".

Nadal has not played since early August when he lost to Lloyd Harris in the third round at the Citi Open, before withdrawing from the US Open due to a recurring foot injury.

The 35-year-old Spaniard had in June pulled out of Wimbledon and the Tokyo Olympics shortly after losing to Novak Djokovic in the French Open semi-finals, saying he was "listening to my body".

Nadal, who will not return this season, has been seen training in Mallorca after last month receiving treatment in Barcelona, offering hope of a return.

"I want to recover from this injury in good condition," Nadal told a news conference.

"I don't know when I will play again, I work a lot every day, I follow a specific plan with a marked roadmap and with very clear objectives."

The next major on the calendar is the 2022 Australian Open to be played in Melbourne in January although Nadal would not commit to participating.

"I will not say what those objectives are, because there are always things that I can't control 100 per cent, but inside my head I'm clear on what my objectives are and I trust that things will follow a positive course," he said.

"Not everything depends on me, but I am confident that my daily efforts will pay off and allow me to return soon."