Losing finalist Rafael Nadal doubts if it's possible for anyone to repeat US Open champ Novak Djokovic's feat of 64 wins and just two losses this season 

Rafael Nadal believes Novak Djokovic's achievements this year will be "probably impossible to repeat" after losing his US Open title to the World No 1. Djokovic won a pulsating final on Monday night at Flushing Meadows in four sets to claim an incredible third grand slam title of the year and fourth of his career. The Serbian has now beaten Nadal in six finals this season and the 6-2, 6-4, 6-7 (3/7), 6-1 victory means he has won 64 of his 66 matches in 2011.

He's up there: Novak Djokovic celebrates after winning the US Open
final against Rafael Nadal on Monday. Pic/AFP

Nadal, who looked to be back in the match after winning the third set on a tie-break, said: "Obviously, I'm disappointed, but this guy is doing unbelievable things... so congratulations Novak and your team for everything.

"What you did this year is probably impossible to repeat. "I try my best in every moment, these kind of matches are very difficult, it brings your body to the limit. "I tried to play great but he always makes a fantastic comeback. That's tennis, I tried my best and am happy with what I did. I ran to every ball and fought until the last ball.

"This year I lost a lot of finals against him but I won a lot in the past and the only thing I can do is try my best every day to keep improving and for sure I will come back next year and try my best." Djokovic now holds the Australian Open, Wimbledon and US Open titles after becoming only the sixth man in the open era to win three of the four majors in the same year.

The 24-year-old spent most of his acceptance speech paying tribute to the victims of the September 11 terrorist attacks after Sunday's 10th anniversary. But speaking about his achievements, he added: "It's an incredible, incredible feeling. "I've had an amazing year and it keeps going but every time I play Rafa it's a big challenge and I want to congratulate him on a great tournament. "I wish we have many more tough matches in upcoming years."