(Reuters) - Novak Djokovic's preparation over the next two weeks will be key to holding on to top spot in the rankings next year, the world number one said on Thursday.

The Serb enjoyed some outstanding form in 2011, winning 41 matches in a row, lifting three grand slam titles and knocking Rafa Nadal off the top of the rankings.

"If I have the right mindset, if I do my preparation in the next two weeks as well as I did in 2011 you know I am confident that I can still play well," Djokovic told a news conference in Abu Dhabi where he is playing in an exhibition tournament.

"And if I could repeat the year I had in 2011, that's something that I can tell you I cannot promise, you know I am looking forward to it. I am enjoying my game now, I have lots of confidence."

Djokovic beat France's Gaels Monfils to set up a meeting with Roger Federer on Friday. The winner will play Nadal or David Ferrer in the final.

"It's always nice to start off the new season with a win but...I was working on something throughout the match, I was trying to find good rhythm. I think I was playing well for this stage," he said.

"I am still not 100 percent on the court, I don't know how I will play tomorrow but it is always a challenge when you are playing Federer."

Djokovic said he had no plans to play any other tournament before defending his Australian Open crown at the year's opening grand slam starting on January 16.

French Open champion Nadal said he planned to become more aggressive next year after losing his world number one ranking.

"Last year I played sometimes a little bit predictable," he said. "My game doesn't have enough surprise for opponents especially the last part of the year.

"I have to play more aggressive, not play every point the same way, concentrate on trying to create opportunities."

(Writing By Alison Wildey; Editing by John Mehaffey)