Here are eight men to watch during the US Open 2019
The world number one is in hot pursuit of his second straight US Open title and third major of the season.
Despite his surprise loss in the semi-finals of Cincinnati Masters, Djokovic is charging up the ranks of the all-time greats.
Having saved two match points to beat Roger Federer in the Wimbledon final, Djokovic increased his haul to 16 Grand Slam titles.
He is now only two behind Rafael Nadal and four shies of Federer's total.
The Spaniard’s toughest challenge these days may be staying fit on the hard courts.
The 33-year-old successfully defended his Rogers Cup title earlier this month but then pulled out of the Cincinnati Masters due to fatigue.
If Nadal, who was forced to retire during last year’s US Open semi-final with knee pain, feels healthy then he could enjoy another run to the title he last won in 2017.
The US Open represents the longest drought of all the majors for Federer, who last won at Flushing Meadows in 2008.
After failing to convert two championship points against Djokovic in the fifth set of last month's Wimbledon final, the Swiss will be desperate to heal his wounded pride by winning a sixth title at Flushing Meadows - and 21st major overall.
Dominic Thiem has struggled to leave a mark at the other three slams, with a quarter-final showing at Flushing Meadows in 2018 being his best effort at a major that is not played on clay.
After falling in the first round at Wimbledon for the second year running, he will be hoping to live up to at least his seeding over the next fortnight.
When the 23-year-old Medvedev took down Djokovic last week en route to winning the Cincinnati Masters, he proved to be the hottest player on the men's circuit after contesting three successive ATP tournament finals.
A maiden Grand Slam title would cap what has already been a remarkable hardcourt season.
Zverev has all the weapons to succeed on the big stage but has so far suffered stage fright every time he shows up at a Grand Slam event.
Two quarter-final appearances at the French Open is the best Zverev has been able to muster at the majors.
Long tipped as a future Grand Slam champion, Zverev needs to step up sooner rather than later if he wants to break the stranglehold of tennis' Big Three of Djokovic, Nadal and Federer - who between them have won the last 11 slams.
Zverev's best showing in New York was a run to the third round last year and have fallen in the first round at Wimbledon this year, he will be eager to avoid suffering the same fate again.
Despite early-round losses Montreal and Cincinnati, Nishikori has been consistent at the majors this year, reaching the quarter-finals of all three and losing only to tennis' Big Three.
As he has been drawn in the same half as Federer and Djokovic, Nishikori will be hoping another grand slam run does not end in the quarter-finals, where he is due to face the Swiss.
What will the Australian do next? Fire another shot at the head of an opponent? Clash with another umpire? Hurl some courtside furniture across the playing surface?
The antics of the bad boy of tennis have overshadowed his on-court performances this year.
Picking up fines for unsportsmanlike conduct seems to be par for the course these days for Kyrgios, who despite his immense talent has yet to win a major.