Andy Murray will have to wait until the last moment to begin the defence of his US Open title but Laura Robson and Dan Evans are both in first-round action in New York later today.
Murray does not expect to play his first-round match against France's Michael Llodra until Wednesday, potentially putting him at a disadvantage compared to his main title rivals.
Rafael Nadal and Roger Federer play today, with Nadal taking on American Ryan Harrison and Federer meeting Slovenia's Grega Zemlja in the night session on Arthur Ashe.
Robson plays in the first match on Court 17 against Spain's Lourdes Dominguez Lino, who has proved a tricky opponent for the British number one in the past.
Robson is seeded for the first time at a grand slam at number 30 and has a lot of ranking points to defend after reaching the fourth round last year, but she will not be piling too much pressure on herself.
That is largely because the 19-year-old has missed the last three tournaments with a wrist injury and only started practising fully a few days ago.
Robson has played just two matches since reaching the fourth round at Wimbledon, and it is the fighting spirit she showed at the All England Club that she hopes will stand her in good stead here.
She said: "I felt at Wimbledon I wasn't playing my best tennis. I played really well against (Maria) Kirilenko and after that it was some scrappy wins and I just managed to get through.
"That gave me confidence in that I don't necessarily have to be playing my best tennis to get through these matches."
Evans has already exceeded expectations by coming through qualifying to reach the main draw of a grand slam for the first time.
His only previous slam experience has come courtesy of two Wimbledon wild cards, where he lost in the first round both times, and he has his work cut out if his is to continue his winning run here.
Evans was drawn against Japanese 11th seed Kei Nishikori, with the pair first up on Court 13 at Flushing Meadows.
The 23-year-old from Birmingham is in the form of his life having won 11 of his last 13 matches, and Murray thinks the match-up could suit him.
The Scot said: "It's a very tough match obviously, but he's not going to get hit off the court.
"He will get into a lot of service games. They both move very well. They're similar heights and build. They're both quick.
"There will be some good rallies. I'm sure he'll learn a lot, regardless of the result. But he will be confident in himself.
"He's won a lot of matches lately and he's won three matches on this surface here. People think sometimes playing a qualifier is a good draw, but it isn't always the case because they are used to the conditions."
Women's defending champion Serena Williams is also in action, opening the night session against Italy's Francesca Schiavone.