Sydney - One of sport's great and enduring rivalries resumes with the battle for supremacy between Rafael Nadal and Roger Federer dominating the new tennis season.
The 2011 campaign got underway this week in Australia, India, Qatar and New Zealand with the first Grand Slam of the season starting in Melbourne on January 17.
Nadal is unchallengeable at the top of the ATP rankings, some 3,305 points clear of Federer, after a superb 2010 season when he took the world number one spot and the French Open and Wimbledon titles from the Swiss star.
By picking up his first US Open title along the way Nadal achieved a career grand slam of winning all the majors by the age of 24.
The Spaniard goes into the new year having won nine major titles and trailing Federer's all-time record of 16.
The pair have faced each other 22 times since 2004 on the tour with Nadal prevailing on 14 occasions.
Nadal modestly plays down the constant debate about who is better although victory in the lucrative UAE exhibition tournament at the weekend has already given the Spaniard an early edge over his rival.
"I think the talk about if I am better or worse than Roger is stupid, because the titles say he's much better than me," Nadal said as the two prepare to clash this week in Qatar.
"So that's true at that moment. I think that will be true all my life."
But such is Nadal's ascendancy at such a young age and five years younger than Federer, that his rate of progress suggests he could surpass the Swiss master by career's end.
"For me, every day and every season start, and I'm going to work to be ready and be competitive to try to be in the top positions to compete to keep winning titles," Nadal said.
"But the pressure for me is going to be the same.
"I try to play well, try to compete against everybody, and try to be in the final rounds."
Federer, who was world number one for 285 weeks before being usurped by Nadal last June, believes his end-of-season ATP World Tour Finals triumph against Nadal will provide him with the springboard to return to the top in 2011.
"I won five titles, won a slam, last year. That obviously makes me be very positive for this year. I believe I can have another great season in 2011," he said.
"I think the men's game is at an absolute high, and having had me and Rafa both making career Grand Slams already at a young age I think is great for the game," he said.
Federer is looking forward to defending the only grand slam title he still holds, the Australian Open.
"I like the pressure of being defending champion. The memories for me back in Australia are very emotional, very nice. I love playing there," he said.
While Nadal and Federer dominate, Serbia's third-ranked Novak Djokovic and Britain's number four Andy Murray, will look to make an impact at the slams.
Djokovic lost to Nadal in last year' US Open final, while Murray fell to Federer in the Australian Open decider.
Denmark's Caroline Wozniacki heads into 2011 as the top-ranked woman, yet without a grand slam title.
Wozniacki won five WTA titles to finish the year-end number one, but is expected to be challenged by three-time US Open champion Kim Clijsters and 13-time grand slam champion Serena Williams this year.
Williams will not be defending her Australian title after a second operation on her foot, which she cut on broken glass in a Munich restaurant in July.
Williams sealed her fifth Australian Open title last January, beating Belgium's Justine Henin in the final.
Former world number one Henin has not played competitively since injuring her right elbow in her fourth round loss to countrywoman Kim Clijsters at Wimbledon last June.