Eight players have a chance to leave the year's last Grand Slam with the world number one ranking, making the Flushing Meadows fortnight that starts Monday a tennis thriller, even without two of the sport's top stars.
Serena Williams is taking time out from the tour to have a baby and Victoria Azarenka is sitting out the tournament, leaving the US Open women's field in total suspense over who might win.
Williams, who won her 23rd Grand Slam title at the Australian Open, announced in April she was pregnant and would miss the rest of the year.
"Serena is always the favorite when she plays and she's at a level on her own when she's playing her best tennis," Denmark's fifth-ranked Caroline Wozniacki said. "But we're here and I think everyone has a shot if they play their best. It's all about playing well for two weeks."
Two-time Australian Open winner Azarenka revealed she is battling with her son's father for custody, and the child thus cannot leave California, so she opted to stay.
Former world number one Maria Sharapova, a five-time Grand Slam champion, will play as a wildcard in her first major tournament since a 15-month doping ban after testing positive for meldonium at the 2016 Australian Open.
And while the Russian's return has been hit by forearm and thigh injuries, she remains a threat
Just ask Romania's second-ranked Simona Halep, who faces her in the first round having lost all six of their prior meetings.
Eight in the running for number one ranking
Czech world number one Karolina Pliskova, Halep, Wozniacki, Wimbledon champion and world number three Garbiñe Muguruza, Ukraine's fourth-ranked Elina Svitolina, Britain's Johanna Konta and Russia's Svetlana Kuznetsova all have a chance to become world number one at the US Open.
Evergreen Venus Williams, the 37-year-old American who has won seven Grand Slam titles and was runner-up this year at Wimbledon and the Australian Open, is ranked ninth but also could become number one again -- by winning the title.
Defending champion and sixth-ranked Angelique Kerber of Germany can't finish the week atop the rankings but she could hoist the crown again as the only past winner from the past decade in the field.
Muguruza aiming to end Flushing Meadows jinx
Muguruza has made herself the bookies’ darling after taking last year's French Open, last month's Wimbledon crown and last week's Cincinnati title. But she hasn't gone past the second round in four tries at New York.
She said in the past, she struggled to find her rhythm at Flushing Meadows.
"I want to change that. I want to find the recipe maybe this year, maybe that I have a little bit more confidence," she said.
Pliskova has taken titles at Brisbane, Doha and Eastbourne this year but has never won a Grand Slam. She reached her only Slam final last year at New York.
"The energy of the city is huge. Obviously love to be coming back there, especially after the fantastic last year," she said.
An early Cincinnati exit sent Kerber tumbling down the rankings race, but the 2016 US and Australian Open champion is feeling the same drive she did a year ago.
"I'm thinking that my fighting spirit is back and I'm feeling that it's getting better and better," Kerber said.
Halep looking for first Slam title
Halep has lost three matches this year when playing for the world number one ranking. But that didn't dim her hopes of claiming a first Slam title at the US Open.
"I will go to New York with the confidence up," Halep said. "I played a really good few months. So I don't have negatives to take."
Svitolina, the youngest in the favored pack at 22, has won titles this year at Toronto, Rome, Dubai, Istanbul and Taipei, and matched her best Grand Slam showing with a French Open quarter-final run.
Wozniacki, the 2014 US Open runner-up and three times a semi-finalist, has lost six finals this year since taking her last title in Hong Kong last year.