Rafael Nadal had the easiest progress into round three of the US Open, but a host of his rivals in the men's singles had to come through marathons on Thursday.
Nadal was awarded a walkover as Thanasi Kokkinakis withdrew from their second-round encounter at Flushing Meadows in New York.
As 18-time grand slam champion Nadal was able to get some valuable rest, Alexander Zverev needed five sets to see off a spirited effort from Frances Tiafoe.
Daniil Medvedev required four sets against Hugo Dellien to keep his title hopes alive as a host of other matches went the distance, including Hyeon Chung's battle with Fernando Verdasco.
Chung came from two sets down and 5-2 down in the fifth to defeat Verdasco, saving a match point to book a meeting with a refreshed Nadal.
Marin Cilic – the 2014 champion – moved on to Arthur Ashe Stadium because of Kokkinakis' withdrawal and defeated Cedrik-Marcel Stebe 4-6 6-3 7-5 6-3.
TOUGH LUCK FOR TIAFOE
Tiafoe has developed an unfortunate habit for losing five-setters, and he was on the wrong end of a topsy-turvy affair with sixth seed Zverev.
German Zverev came through 6-3 3-6 6-2 2-6 6-3, leaving Tiafoe to bemoan another marathon effort in vain, having also lost to Fabio Fognini in five sets at Wimbledon.
Asked to summarise his grand slam year, Australian Open quarter-finalist Tiafoe said: "Paris, unfortunately got sick there. Then I lose to Fabio in five. I lose to Zverev in five. You tell me how that feels. It's tough."
Zverev next faces Aljaz Bedene – a five-set victor over Benoit Paire. Alexander Bublik, Kamil Majchrzak and Paolo Lorenzi all won after going the distance.
Lorenzi latter's clash with Miomir Kecmanovic lasted four hours, 48 minutes and the Italian now has to gather what energy he has left ahead of Friday's meeting with 2016 champion Stan Wawrinka, who defeated Jeremy Chardy 6-4 6-3 6-7 (3-7) 6-3.
Wawrinka and Lorenzi's match precedes Medvedev facing Feliciano Lopez, who came from a set down to beat Yoshihito Nishioka 6-7 (7-9) 6-0 6-4 6-4.
DUBIOUS REWARDS FOR EVANS & KUDLA
Dan Evans and Denis Kudla each knocked out seeds in Lucas Pouille and Dusan Lajovic, and both received dubious rewards for their performances.
Evans will have a tight turnaround to face third seed Roger Federer on Friday, while home hope Kudla will take on defending champion and world number one Novak Djokovic.
John Isner enjoyed a straightforward win over Jan-Lennard Struff, Gael Monfils also enjoyed serene progress against Marius Copil as he set up a match with Denis Shapovalov, while David Goffin eased past Gregoire Barrere 6-2 6-2 6-2.
Next up for Goffin is Pablo Carreno Busta after the 2017 semi-finalist beat Ricardas Berankis 6-4 6-7 (3-7) 6-2 6-0.
AUSSIES ON SONG
Nick Kyrgios had no problems against Antoine Hoang, winning 6-4 6-2 6-4 to secure a third-round clash with Andrey Rublev, the beneficiary of a walkover after one set with Gilles Simon.
Fellow Australians Alex de Minaur and Alexei Popyrin were also triumphant, though Jordan Thompson lost to Matteo Berrettini.
Kyrgios expressed no surprise at the success of his compatriots. He told a media conference: "De Min, I never expect anything less from him, he's an absolute warrior. He can beat a lot of good players.
"When I see him progressing through a draw, I know it's a nightmare for anyone who comes across him.
"Obviously Popyrin had a pretty good win today. Kukushkin is a savvy veteran. I'm not surprised when those guys win matches at all. They're capable of doing some big things."