Alexander Zverev made his long awaited first grand slam quarterfinal, and no one can say the German did it the easy way. Indeed call him the French Open's marathon man.
But marathon woman Caroline Wozniacki -- she finished the New York City Marathon in 2014 -- trailed Daria Kasatkina 7-6 (7-5) 3-3 when darkness halted proceedings at around 9:20 p.m. Paris time.
Zverev beats Karen Khachanov 4-6 7-6 2-6 6-3 6-3
His third straight win in five sets
Caroline Wozniacki trailed Daria Kasatkina by a set
Novak Djokovic, Dominic Thiem, Madison Keys also through
For the third consecutive round, Zverev rallied from a 2-1 deficit in sets and this time it came against a friend from his junior days, Karen Khachanov.
It wasn't as dramatic as his previous tussle when the second seed saved a match point against Damir Dzhumhur, but the 21-year-old found himself in trouble in the fourth set Sunday prior to defeating the unseeded Russian 4-6 7-6 (7-4) 2-6 6-3 6-3.
He was joined in the men's quarterfinals by Dominic Thiem, his next opponent, and the rejuvenated Novak Djokovic.
At 2-2 in the fourth, Zverev saved two break points and then broke for 4-2 after Khachanov led 40-15 on serve.
When the match ended on court Suzanne-Lenglen, Zverev sunk to his knees with arms outstretched.
Asked later about finally achieving the last eight at a major -- he has won three Masters titles and makes regular appearances in quarterfinals at ATP events -- Zverev offered up a mixture of sarcasm and humor, which is nothing new.
"I'm very pi**ed off about it," he smiled. "I want to be home right now.
"I'm happy. But this is not the end. This is the quarterfinals."
Vows to be ready
Zverev has shown his mental toughness and physical stamina in reversing the deficits in Paris.
And in typical Zverev style, he vowed to be "ready" for his crunch clash with Thiem.
"I'm in the quarterfinals of a grand slam. If you're mentally fatigued, then something is wrong with you," said Zverev, the youngest men's quarterfinalist at the French Open since Juan Martin del Potro in 2009. "Physically, obviously it's not easy to play back to back to back five-set matches, but I will manage it somehow.
"I will make sure to be ready in two days' time."
Thiem has been even more impressive considering the opponents he encountered.
He overcame the dangerous Stefanos Tsitsipas in four sets in the second round, for example, and passed an even more difficult test Sunday from Kei Nishikori.
The Austrian blew the Monte Carlo finalist away in the first two sets, lost the third, but came through 6-2 6-0 5-7 6-4 to land in a third consecutive Roland Garros quarterfinal.
Thiem stumbled in the Madrid Masters final to Zverev last month, though given the stage, their respective forms and the latter's time spent on court, the seventh seed goes in as favorite.
"I think it's the matchup most of the fans in Germany and Austria were hoping for when they saw the draw," said Thiem.
Most neutrals, too.
Thiem is keen to progress even further and to a maiden French Open final after being convincingly knocked out in the semifinals the previous two seasons by Djokovic and Sunday's birthday boy Rafael Nadal.
"I think for me it's time to move on to make a great step, because I'm turning 25" in September, said Thiem. "I'm not that young anymore. That's (Zverev's) part. He's only 21."
Wozniacki is a tour veteran at 27 and to her delight, won't ever be asked again when she'll win a first major after breaking through at the Australian Open in January. Hard courts certainly are to the world No. 2's liking, with clay bringing less success. Wozniacki did however make the quarterfinals last year in Paris prior to losing to the eventual champion Jelena Ostapenko.
Kasatkina doesn't possess Ostapenko's power but she owns a varied game with her share of power and spin.
The bubbly 21-year-old made the biggest final of her career in Indian Wells in March, beating Wozniacki en route. Sunday evening she rallied from 5-3 down in the first set, which lasted 68 minutes.
Both players wanted play suspended as light faded just after 9 p.m. but were told to continue by tournament officials, to the crowd's delight. Twenty more minutes elapsed before the duo went off.
Djokovic eased past Fernando Verdasco 6-3 6-4 6-2, although the early stages on Philippe-Chatrier court suggested a lengthy battle. The first three games lasted close to 30 minutes.
The 12-time grand slam winner's next challenger isn't David Goffin but rather Marco Cecchinato, who upset the ailing eighth-seed 7-5 4-6 6-0 6-3 after losing to the Belgian last month.
On Saturday, Goffin saved four match points to complete a draining victory over Gael Monfils.
Cecchinato -- who trailed by two sets in his opener -- has enjoyed quite the rise since the end of April, when he won the Budapest title as a lucky loser to help his ranking rise to its current 72nd.
Two years ago Cecchinato was cleared of match fixing after initially being given an 18-month ban by Italy's tennis federation.
Grand slam quarterfinal sweep
Americans Madison Keys and Sloane Stephens have now advanced to the quarterfinals at all four majors after their comfortable wins over Mihaela Buzarnescu and Anett Kontaveit, respectively.
Keys prevailed 6-1 6-4 and hasn't dropped a set on the surface she finds the most challenging.
Having escaped Saturday -- 8-6 in the third set over Camila Giorgi -- Stephens had a surprisingly simpler time in the fourth round, easing past 25th-seed Kontaveit 6-2 6-0. Kontaveit upset Petra Kvitova on Saturday and flourished ahead of Roland Garros.
Stephens -- who plays either Wozniacki or Kasatkina on Tuesday -- snapped an 0-for-4 skid in French Open fourth rounds.
Keys said she was looking forward to Monday's blockbuster between Maria Sharapova -- they share the same agent, Max Eisenbud -- and Serena Williams.
Williams leads the series 19-2.
"I'm obviously a tennis fan just like everyone else, so I think I'm just as excited to see that match," said Keys.
Nadal, meanwhile, is bidding for yet another win at Roland Garros.
A straight-set win over Germany's Maximilian Marterer and the 10-time champion would make it 37 straight sets in southwest Paris.