NEW YORK -- Eight years after playing one of the most memorable -- and surprising -- US Open men's singles finals, No. 3 seed Roger Federer and Juan Martin del Potro will meet again in Arthur Ashe Stadium. It's a quarterfinal match and -- who knows? -- Federer might win this time.
Much has happened since del Potro upset Federer on that sultry September night in 2009.
Back in '09, Federer was at the peak of his powers, going for a record sixth consecutive US Open title to add to the French Open and Wimbledon titles he'd won earlier in the year. Del Potro was just a 20-year-old Argentine in a sleeveless shirt that left his entire right arm free to fire those lethal forehand missiles.
Federer won the first set and built a 5-4, 30-love lead in the second. A blowout was in the making. But Delpo broke serve, won the set and went on to win his first -- and thus far only -- major.
Federer is 36 now and in the midst of a credibility-straining renaissance. Del Potro is 28 and fighting his way back toward the top once again. In the last round, the No. 24 seed mounted one of the most memorable comebacks in recent Grand Slam history. Dominic Thiem humiliated del Potro for two sets, but, with a frenzied crowd at his back, del Potro ultimately won in five.
That begs the overarching question: Will del Potro have the energy, strength and stamina to rebound from that brutally physical match on just one full day's rest? Federer has cruised easily through his past two matches without dropping a set. He leads their head-to-head series 16-5.
Here's a look at the other three quarterfinals:
No. 1 seed Karolina Pliskova vs. No. 20 CoCo Vandeweghe (series tied at 2-2)
Vandeweghe, having conquered her fear of majors, is inching ever closer to the head of the gifted U.S. women hoping to crack the Grand Slam code. As late as 2015, she had never won two matches at a Grand Slam event; heading into this year's Open, she made a semi (Australian Open) and another quarterfinal (Wimbledon). She's becoming a big-stage player.
Vandeweghe is a little more explosive and athletic than Pliskova. The American can win this if she keeps her unforced errors down and her emotions under control.
Pliskova is the defending finalist, and her power baseline game is falling into place. The pressure she felt coming in has largely been alleviated.
They've split their four meetings, all of which were straight-set matches.
No. 1 seed Rafael Nadal vs. No.53 Andrey Rublev (first meeting)
Like Federer, Nadal has overcome some early-round jitters and shortcomings in his game. It's a good thing, too, because he's facing a 19-year-old Russian player who is playing as if he has nothing to lose. Which he doesn't.
Rublev was awarded a "lucky loser" chit into the main draw at Umag in mid-July and proceeded to win the tournament. He has been stellar again, hammering out quality wins in New York against two seeds, No. 7 Grigor Dimitrov and No. 9 David Goffin.
Rublev grew up worshipping Nadal, to the point that he even dressed like Rafa, buying every new Nike outfit Nadal wore. The other significant edge for Nadal is that Rublev, a junior French Open champ, is mainly a clay-proficient baseliner, the kind Nadal has seen and beat a thousand times in his career.
No. 15 Madison Keys vs. No. 421 Kaia Kanepi (Kanepi leads, 1-0)
That ranking preceding Kanepi's name is no typo. Once ranked No. 15, thanks largely to her powerful groundstrokes and big serve, she fell prey to a combination of slump and injury. Kanepi took nearly a year off before she returned to competitive play in early June this year.
During her sabbatical, Kanepi went to a Finnish school that teaches driving on icy roads. Perhaps that experience will help keep her from sliding down a slippery slope when she meets an opponent who has a hot hand and will be playing in front of a vocal home crowd on Ashe.
Expect Keys to play with confidence after her fourth-round comeback win against No. 4 seed Elina Svitolina. Both Keys and Kanepi will be cracking big shots, but it's hard to imagine Keys failing to capitalize on this enormous opportunity to make her second Grand Slam semifinal.
Kanepi's win in their only previous meeting was on red clay more than two years ago.