Nadal, 31, and Federer, 36, have never faced each other on the NY hardcourts but could meet in the semi-finals. One wrinkle sweetens the thought: Despite having faced each other 12 times at the majors, the pair have never played at the U.S. Open.
The 31-year-old Spaniard has re-ascended to No. 1 in the world after compiling a 49-9 record in 2017 with four titles, including his 10th French Open crown and 15th Grand Slam title in June.
Five top 11 men's players are among those who have said they will miss the year's final grand slam, which starts on Monday in NY: former world number one Djokovic (elbow), Andy Murray (hip), 2016 champion Wawrinka (knee), Canada's Milos Raonic (wrist) and Japan's Kei Nishikori (wrist).
Unpredictable Australian Kyrgios has shown signs of delivering on his potential this year, most recently when beating Nadal in the quarter-finals in Cincinnati before losing to Bulgaria's Grigor Dimitrov, another U.S. Open title candidate, in the final.
Ellenbecker said after matches, a player's focus shifts immediately from performance to recovery, which means replacing fluid and vital nutrients and for some, ice baths, compression garments and other recovery methods that work for them. "A lot of points and games to play, so now is not the moment to think about that".
The other half of the men's draw is more wide open-the injured Andy Murray announced he was out on Saturday-and that's just what 20-year-old Alexander Zverev could have wanted most.
Chances are he'll do that, and possibly a lot more, at the Open.
United States 10th seed John Isner, the top-ranked player in his quarter of the draw thanks to a reshuffling when Britain's Andy Murray withdrew due to a hip injury, opens against France's Pierre-Hugues Herbert. He has been playing well and has a nice draw.
In the women's draw, there's one doozy to start the tournament: Simona Halep, seeded second, against the unseeded Maria Sharapova, who received a wildcard as she returns from a 15-month drug suspension.
Sharapova is 6-0 against Halep over their careers and 10-0 in first-round matches at Flushing Meadows.
"It's going to be a big challenge, first round of a Grand Slam, to face her", Halep said.
The Romanian is much improved, although she can get uptight on the big occasion: three times this summer she has lost matches that could have taken her to world No 1. You could forsee that maybe, you know, Rafa and me would be back in some shape or form, but maybe not quite like this.
My advice: Don't feel bad for Halep.
Former World No 1 Sharapova made her return in April at Stuttgart, reaching the semi-finals as a wildcard, but such invitations sparked criticism from some WTA rivals, saying she should have to work her way back without such benefits, some suggesting a life ban. After the hard first round, Halep would have an open event until the quarterfinals, where she could meet Great Britain's Johanna Konta.
At 37, she's playing some of her best tennis, reaching the finals of the Australian Open and Wimbledon.
KYLE EDMUND v Robin Haase (4pm United Kingdom time): Britain's No 2, who made the 4th round here a year ago, takes on the often flaky 32nd seed. Also in the mix are Angelique Kerber (last year's champion), eighth seed Svetlana Kuznetsova, tenth seed Agnieszka Radwanska and fifteenth-seed American Madison Keys. They occupy center stage while Andy Murray and Novak Djokovic have retreated from NY to tend to a niggling left hip, for Murray, and a right elbow, for Djokovic.