Novak Djokovic of Serbia celebrates after defeating Rafael Nadal of Spain in the men's final of the U.S. Open tennis tournament in New York, September 12, 2011.  [Photo/Agencies]

BEIJING - With three Grand Slam and five Masters titles, the world number one ranking, a 70-6 win-loss record and a record prize money haul of 12.6 million US dollars, Serb Novak Djokovic was arguably the king of tennis in 2011.

He has been unbeaten in 43 matches in the first half of the season, dating back to the Davis Cup final in December 2010, until that run ended against 16-time Grand Slam champion Roger Federer in the French Open semifinals.

The streak brought him the second Australian Open title and all the season's opening four Masters at Indian Wells, Miami, Madrid and Rome, defeating Rafael Nadal in the finals of all of them.

The loss to Federer at the French Open did not dent Djokovic's self-belief and after taking a brief break, he went back on the winning track.

The Serb defeated Nadal to win Wimbledon and ended the Roger-Rafa duopoly at the All England Club in the past eight years. In the process  Djokovic also took the Spaniard's world number one spot.

In the US Open final, Djokovic destroyed Nadal again after he had rallied past Federer from two sets, and two match points down, in a breathtaking semifinal.

Djokovic, who had ended each season ranked No. 3 in the world behind Federer and Nadal for four long years, admitted at times that he used to be "a little bit" frustrated when Federer and Nadal were at the top of men's professional tennis, but he now realizes it has been part of a learning process as a sportsman.

"They have been the two most dominant players in the world the last five years. They have won most of the majors we are playing. So sometimes it did feel a little bit frustrating when you kind of get to the latter stages of a Grand Slam. They always come up with their best tennis when it matters the most," said Djokovic.

"But it's a process of learning, a process of developing and improving as a tennis player and just finding the way to mentally overcome those pressures you have. I always believed that I had the quality to beat those two guys," the 24-year-old added.

The figures back up Djokovic's confidence. He beat Nadal six times out of six, Federer four out of five and world number four Andy Murray, two in three, with the Briton's win coming courtesy of an injury retirement in the final in Cincinnati.

Djokovic's backhand is the best in the business and his return is also in a class of his own. But unlike his predecessors at the top of the game, his success isn't dependent on those one or two factors, rather a combination of technical acumen, consistency, a suffocating array of athleticism, effective defense and movement.

His major opponents, however, were unable to figure out how Djokovic achieved that feat. They even could not notice the change Djokovic has made.

"Everybody knows how good Novak is and how good he can be, but he was the same a few years ago," Nadal said.

Federer echoed the Spaniard's opinions. He said: "He had some tight matches that he could have lost. I don't believe he's different from my point of view.  Maybe he's winning easier than before."

The Serb was troubled by fatigue and health problems and conceded four defeats in the closing stages of the year, but he still felt proud of the best season he ever had in career.

"I had an unbelievable year. Nothing can really ruin that. I will always remember this year as the best of my life."

Djokovic said he has enough time to get prepared ahead of the new season and has set his sights on doing it all again next year.

"This year's success gives me a reason to believe that I can win again. Why not?"

"I think it doesn't make any sense to be anything other than optimistic. I need to believe in my qualities and my abilities and I need to believe that I can repeat the success."