MADRID, Oct 19 (Reuters) World number three Novak Djokovic has proved he can play at the same level as Rafael Nadal and Roger Federer after breaking into the elite this year.
But the 20-year-old Serb, who reached the Madrid Masters quarter-finals yesterday, said he believed his biggest challenge was to maintain his form next season.
''This year I've made incredible achievements and, looking at my results this year, I've had enough reasons to believe thatI'm on the level they are right now,'' he said after beating Juan Carlos Ferrero to reach the last eight.
''I've showed I've enough quality but this is only one year, this is my breakthrough year and it's an amazing year but they (Federer and Nadal) have been at the top of the standings for three or four years.
''It now all depends on my next year. I need to have a lot of rest after (November's Masters Cup in) Shanghai to prepare well for the upcoming year because I truly believe I can be a big challenger for that first place in the next couple of years.
SAME LEVEL ''I cannot be sceptical about my second year but I need to be ready. We have a lot of situations when players were doing really well one year and the next year not doing so well.
''I have to take it really seriously and try to remain on the same level and be consistent with the results.'' Djokovic, who has won five titles this year and also reached the US Open final, is one of four players who have already qualified for the season-ending Masters Cup starting on November 11.
He admitted the success had taken its toll, but was confident he could still finish the season strongly.
''I've had a long season and I'm very exhausted physically and mentally but I believe I can do well in this tournament.
''My goal for this year is to play well in the important tournaments, in Paris and then Shanghai which is the most important tournament for me.'' Djokovic, who had to stave off a strong fight-back from Ferrero in his third round match, takes on Croat Mario Ancic in the quarter finals at the Madrid Masters today.
Reuters BJR GC1430