Nadal is in the other half of the draw to Federer and Djokovic and is seeded to meet Juan Martin del Potro in a repeat of last year's semi-final. Has points to defend after reaching the fourth round past year.
Being the defending champion, the Spaniard would surely want to retain the title and win it for the fourth time.
Fast forward three months and Djokovic is once again the man to beat.
"It's a wonderful feeling".
Halep has been playing with confidence since winning the French Open and her preparations for the U.S. Open included a win at Montreal before reaching the Cincinnati final, though she pulled out from CT to rest an Achilles injury.
Andy Murray, playing his first Grand Slam since Wimbledon of past year and still battling to regain full fitness in the wake of January hip surgery, was handed a relatively gentle return to the major stage, drawing Australian James Duckworth, ranked 445th in the world, in the opening round. The ball doesn't fly as much at the US Open; Federer said the ball was "extremely bouncy" this year, more than usual.
"The courts suit my game, and I love being in NY".
"He's a great champion", said Federer in praise of Djokovic in Cincinnati.
Anderson burst through the tournament to make his Grand Slam final debut at Flushing Meadows previous year at the age of 31, only to be crushed in straight sets by Rafael Nadal.
Since August a year ago, the No 1 ranking has swapped hands between Nadal and Federer four times, as the two remain atop the ATP rankings. The 26-year-old arrives in NY without the risk of losing her world No. 1 ranking, because even if second-ranked Caroline Wozniacki goes all the way, she will not accumulate enough points to overtake her.
Federer also knows that the clock is ticking.
It's been 10 years since Roger Federer's last US Open in 2008.
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Now 37, Federer would become the oldest NY champion in the Open era should he lift the trophy again on September 9 and second oldest of all time.
2002: Pete Sampras closed his career in storybook fashion as he defeated Andre Agassi in four sets for his fifth US Open title.
It was his earliest exit at the All England Club in five years.
'It's even a bigger priority this year, the US Open, than it has been last year, ' he added.
He's never been that close to winning the US Open since, just once reaching the final.
Despite last year's lopsided victory, Nadal said Anderson would pose a serious threat.
If you look at the pathways both players would take towards the final, the road is much easier for Nadal. His comeback has been far from smooth after spending nearly a year on the sidelines and has played only seven matches since his return.
"The last couple of days (before the tournament) is the moment to understand, that you really realize if you are better, you are worse - when you start to put the full mind on what you're doing".
Amongst the widely-hyped "Next Gen", world number four Alexander Zverev is still a work in progress. Even skipped the French for that.
He has hired Ivan Lendl - who took Murray to the 2012 title - as his new coach.
Having failed to defend his Wimbledon crown after being knocked out by Kevin Anderson in the quarter-finals, the Swiss star then lost to Novak Djokovic in the final of the Cincinnati Masters.
Murray later lost to Lucas Pouille in the first round of the Cincinnati Masters, which drew a lot of concern because of the way he lost it, but Murray recognised just how close he came to beating a Top-20 player in the Frenchman.