The fourth-round line-up is locked in at the US Open after an incredible six days of play at Flushing Meadows.
We look back at some of the more notable storylines so far, which have helped set the stage for an unmissable second week in New York.
Djokovic, so far, handling the pressure
The world No.1 arrived at the tournament having positioned himself to achieve the greatest feat in tennis – winning all four major titles in a single season.
The last time we saw a player on the brink of such an achievement was six years ago, when Serena Williams progressed to the 2015 US Open semifinals. But she simply could not play freely given the incredible history at stake, and fell in a shock defeat to unseeded Italian Roberta Vinci.
Despite some wobbles of his own, Djokovic has, so far, managed to remain on course; after dropping the first set to Kei Nishikori in the third round, he largely dominated the contest to move to within four wins of the calendar Slam.
?? let’s goooooooo #USOpen pic.twitter.com/LMG2pca51R
— Novak Djokovic (@DjokerNole) September 4, 2021
“After I won in Paris this year, I felt like, 'OK, I like my chances on grass…' It did not seem impossible any more to go for all four in a row in the same year,” said Djokovic, who next faces American world No.99 Jenson Brooksby.
“So here I am. I'm in a good position to do that. Still in the tournament. But I've got to take one match at a time.”
The future is bright
In a series of deflating pre-tournament announcements, Roger Federer, Rafael Nadal and Serena Williams revealed they would not participate at the US Open. Former champions Venus Williams and Stan Wawrinka also withdrew.
But while we must accept these legendary veterans are closer to the end of their careers than the beginning, into the void at this year’s tournament stepped a trio of exciting teenaged talents.
On Friday in back-to-back matches on Ashe, Spain’s Carlos Alcaraz stunned Stefanos Tsitsipas in a fifth-set tiebreak before Canadian Leylah Fernandez ousted defending champion Naomi Osaka.
A day later, Brit Emma Raducanu joined her fellow 18-year-olds in the last 16 after thoroughly dismantling Sara Sorribes Tormo.
“I think that to have so many young players coming through is just really great for the game, because it just shows how strong this next generation is,” Raducanu said.
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“I think that having so many young players and 18-year-olds, I think we all inspire each other to play better. Because like for me today, I wanted to join them in the second week as well, so that was an extra bit of motivation.”
Also through to the fourth round are compelling 20-year-olds Iga Swiatek, Jannik Sinner and Brooksby, plus Canadian 21-year-olds Bianca Andreescu and Felix Auger-Aliassime.
Women’s draw catches fire
In a 20-year first since the introduction of the 32-seed system at Grand Slam tournaments, all women seeded in the top 20 progressed to the third round at Flushing Meadows.
And what happens when the best players keep winning and progressing? They eventually play one another.
“At the dinner we were watching on the schedule, and I was, like, every match is a semifinal,” smiled Simona Halep, discussing Friday’s third-round schedule. “Everybody is super strong. The matches are great, in my opinion, for everybody.”
Battles between major champions Garbine Muguruza and Victoria Azarenka, and Angelique Kerber and Sloane Stephens, were particular highlights.
And it’s no different in the fourth round, with Muguruza next up against reigning Roland Garros champion Barbora Krejcikova, Halep facing Elina Svitolina, and Swiatek taking on Belinda Bencic – just to name a few.
Even with Osaka and world No.1 Ash Barty bowing out in round three, the second week of the women’s event promises plenty.
Men’s draw unusually open
So too does the men’s event – but in this case, it is because fresh faces have emerged.
With only four of the top 10 seeds remaining in the last 16, pockets of the men’s draw have opened up for qualifiers, or in-form youngsters waiting to strike.
Oscar Otte joins fellow German Peter Gojowczyk and Botic van de Zandschulp as Qs in #USOpen 4R.
— ATP Media Info (@ATPMediaInfo) September 4, 2021
* 1st Q trio in Grand Slam 4R since 1995 @RolandGarros (Draper, El Aynaoui, Voinea)
* 1st Q duo from same country in Grand Slam 4R since 1993 @AustralianOpen (Garner, Jones of USA)
Daniil Medvedev is the only top-10 player left in the bottom half, where his projected semifinal opponent is one of either Auger-Aliassime, Alcaraz, Frances Tiafoe or Peter Gojowczyk.
Djokovic, Alexander Zverev and Matteo Berrettini are big guns still alive in the top half and look set to advance further, but after the shocks of the first week, perhaps nothing can be guaranteed.
Momentum matters
Several players enjoying purple patches have carried this form into the fourth round at Flushing Meadows.
Zverev – 14-match winning streak
Djokovic – 23-0 at Grand Slams in 2021
Berrettini – 28-5 since Monte Carlo
Krejcikova – has won 28 of her past 31 matches
Medvedev – has won 21 of his past 24 matches
Pliskova – has won 18 of her past 22 matches
Kerber – has won 17 of her past 19 matches
Raducanu – has won 17 of her past 21 matches
Bencic – 12-1 since Wimbledon
Whose momentum will last the course?
We will find out in the coming days as the US Open's second week unfolds.