Rafael Nadal has no timeline for his return to competitive tennis but on Tuesday the world number four did not completely rule out the possibility of returning from injury in time for next month's Davis Cup and ATP World Tour finals.

Nadal has not played since suffering a shock second-round Wimbledon defeat to Czech Lukas Rosol in June and has yet to return to the practise court, but the 26-year-old Spaniard left the door open for a comeback before the end of the season.

He conceded, however, that the chances of appearing at the ATP World Tour final in 26 days or helping Spain against the Czech Republic in the Nov. 16-18 Davis Cup final were remote.

"Impossible, no. But difficult, yes," Nadal said during a conference call to promote his participation in an exhibition match against Juan Marlin del Potro in March.

"I want to go day-by-day, I go every day to the gym, the swimming pool to continue with my recovery. I am trying not to think that far."

The winner of 11 grand slam titles, including a record seven French Opens, Nadal missed the London Olympics and U.S. Open as he fights to undo some of the damage inflicted on his fragile knees from years of competing on hard courts.

Nadal spends his days in the gym, swimming and undergoing therapy treatments but, while he acknowledged feeling some improvements, he is not ready to hit the practise court.

"It has been very, very tough for me because I feel that my knee didn't improve in the right way... but the last couple of weeks the improvement in my knee is something that I can really feel," said Nadal. "That helps me to keep working hard doing every day what I

have do.

"I am working to try to comeback to practise on the tennis court in a not very long period of time."

Progress has been frustratingly slow but Nadal maintained he is not going to rush his return.

He has dealt with injuries several times throughout a career that has included a record 21 World Tour Masters lilies and an Olympic gold medal but has entered uncharted territory with the length of his current layoff which has left him unsure what to expect or when he will be back to full fitness.

"Thai is something I will know when my I feel my knee completely without pain when I start to practise," said Nadal. "1 didn't have in the past this long period of lime outside of the tennis court, outside of the competition.

"I can imagine when I come back I will need time practise and practise more and more every day, maybe that will take one month and a half."