Once the hunter, now the hunted, Andy Murray is braced for an all-out assault on his US Open title from rejuvenated Rafael Nadal and world number one Novak Djokovic.
Murray ended Britain's 76-year wait for a Grand Slam men's champion by triumphing in New York in 2012 and backed it up with his historic Wimbledon victory this year, the first by a British man since Fred Perry in 1936.
The Scot beat Djokovic to win the US Open 12 months ago and repeated the dose against the Serb at the All England Club six weeks ago.
But it is Nadal, rather than Djokovic, who is tipped to win a second title in New York, to add to his 2010 victory, and clinch a 13th career major.
The 27-year-old Spaniard missed the 2012 tournament as he rested his troublesome knees, part of a seven-month injury lay-off which stretched from the second round at Wimbledon to Vina del Mar in Chile in February.
Since his return, Nadal has racked up nine titles, including five Masters, and boasts a win-loss record of 53-3.
His only blip was a first round trauma at Wimbledon, his bitter-sweet relationship with grass courts rekindled far too quickly after the draining march to an eighth French Open just two weeks earlier.
Nadal's title in Cincinnati followed victory in Montreal -- the last man to clinch that Masters double was Andy Roddick in 2003 who also went on to claim the US Open.
"Last year I watched this event on the TV. This year I have the chance to be here. That's great. All of that is fantastic for me," said Nadal, who boasts a 16-0 record on hard courts in 2013.
"It's been great this year, but it's no time to think about what happened. Now I have a chance to compete with the right attitude. I can lose, I can win."
Nadal, who faces American wildcard Ryan Harrison in the first round, has supplanted Murray as world number two since Cincinnati after finding himself relegated to five when he reappeared in Chile.
Murray's post-Wimbledon party has fallen flat in recent weeks with a third round loss to Ernests Gulbis in Montreal followed by a quarter-final exit to Tomas Berdych in Cincinnati.
But Murray, 26, has been here before -- 12 months ago, he arrived in New York having suffered third round defeats in both Toronto and Cincinnati.
The Scot begins the defence of a major for the first time with an opening match-up against French veteran Michael Llodra.
"I think there is less pressure. I think before the first match there will be nerves because it's a new experience and it's different," admitted Murray on Saturday.
"But I think once the tournament gets going, I don't think it changes. There was a lot of pressure on me for a lot of years to win a Grand Slam, and then same sort of thing at Wimbledon. I wouldn't imagine it would be the same here.
Djokovic, whose first round opponent is Lithuania's Ricardas Berankis, a former world junior number one, heads for New York with the focus squarely on Nadal as well as the worrying decline of Roger Federer.
The Serb, who beat Murray to retain his Australian Open title this year, came agonisingly close to ending Nadal's French Open domination in an epic Paris semi-final before being out-played by Murray in the Wimbledon final.
The 26-year-old has made the US Open final in each of the last three years and was champion in 2011.
He believes Nadal is the New York dangerman.
"Nadal is definitely back, and he's playing maybe the best tennis that he ever has played on hard courts," said Djokovic on Saturday.
Federer, 32, heads into his 14th US Open at seven in the world, his lowest ranking for 11 years.
The 17-time major winner has already been defeated 11 times in 2013, including a second-round loss at Wimbledon which ended his record of 36 successive Grand Slam quarter-final appearances.
A five-time US Open champion, Federer's last final appearance in the city was in 2009 where he was defeated by Juan Martin Del Potro.
But despite his slump, the Swiss star, who tackles Slovenia's Grega Zemlja in the first round, believes he can still be a factor at the Grand Slams.
"It's important that I concentrate on my game and that the passion is there, that I work the right way, that I'm prepared, and then I feel like I can win a tournament," said Federer.