Rafael Nadal has vowed to put "a tough year" laced with anxiety behind him as he prepares for a return to Grand Slam winning ways in 2016.

A round-of-32 defeat to Fabio Fognini at the US Open this year meant Nadal had failed to mark a tennis season with a Grand Slam trophy for the first time since 2004.

The Flushing Meadows exit had followed a disappointing time at Wimbledon - he lost to 102-ranked Dustin Brown - though he had at least reached the quarter-finals at both the Australian and French slams.

With several tournaments kicking off in Asia, Nadal can expect to be fighting again for ATP titles, while his overall focus is now shifting to next season, when he can hope to make it a second Australian Open title - the only grand slam trophy he has just one of.

"It was a tough year, because I was playing with too much anxiety for a lot of motnhs, especially at the beginning of the season," said Nadal, who will also hope to be involved at the season-ending ATP World Tour Finals in London.

"Now I feel much better about that. Not a hundred per cent fix, but much better. I'm close to being 100 per cent fixed. And I am enjoying being on a tennis court, the practices, the competition.

"During the first five, six, seven months of the season I was feeling very tired. Every time I was playing, every time I was practising, something pushed me here, nerves, anxious, probably the injury of last year...I suffered this year for those months.

"But last couple of months I'm enjoying. I really believe that I'm going to be ready for next year. I don't know if I can win another Grand Slam, I don't know if I can do it, but I believe I can do it.

"If that happens - and I believe that's going to happen soon because I feel much better - I'm going to find my level of tennis."