Rafael Nadal is looking for the one major title to elude him when he takes part in the ATP World Tour Finals, beginning Sunday in London.
But the 24-year-old will have his work cut out in the season-ending showcase, with the field at London's O2 Arena consisting of the world's eight best tennis players.
The indoor event may not suit the world number one, and he feels the tournament is the toughest of the season to win.
"For me personally it's more difficult to win four matches indoors than to win seven matches in a grand slam," the Spaniard said.
"The problem is that the bounce is low and it feels like the ball is dead. The ball has no life. When there is a big bounce, it is easier for me to play well."
"This is probably the most difficult tournament for me to win during the year."
Nadal made a slow start to 2010, but once he got going he added a fifth French Open, a second Wimbledon title and a maiden US Open crown to his burgeoning trophy cabinet.
Nadal said it is hard to believe he arrives in London having won three out of the four Grand Slam titles this year, given his injury-ravaged 2009 campaign, and he credits the turnaround to his win in Monte Carlo in April.
"After that, everything was a little less difficult, I played with more calm, more confidence," he said.
"I started the season playing very well. In Australia I had an injury but I had a good match against Andy (Murray). After that I felt ready to compete against the best players."
"For sure winning three grand slams was something that was impossible to imagine, but it happened and I enjoyed that and now it's about keeping working hard to keep having chances to win tournaments."
Nadal opens his ATP World Tour Finals campaign with a clash against American Andy Roddick on Monday.