Rafael Nadal might have looked like his old self in the first three rounds of the US Open, but in round number four, the No.4 seed ran into an inspired Lucas Pouille, who outlasted the Spaniard in a thrilling five-setter at the Arthur Ashe Stadium on Sunday.
Pouille is seen as one of the players capable of taking over the mantle once the "Big Four" of tennis bid their goodbyes, and the Frenchman showed his talent in spades against the 14-time Grand Slam champion, eventually prevailing 6-1, 2-6, 6-4, 3-6, 7-6 (8-6) in three hours and seven minutes.
With the match tied at two sets, Nadal had plenty of opportunities to book his place in the quarterfinals, going up a break at 1-0 and 4-2, but every time the fourth seed looked like having the match in the bag, Pouille fought back.
That meant the match going level at 6-6, with both players having won 156 points each, and with the US Open not having the "fifth set you continue playing till someone wins conventionally" rule, it meant a tiebreak.
Much like Nadal will look with regret at the opportunities missed in the final set, the left-hander will wonder just how he mishit an easy forehand in the penultimate point of the match, which would have given him the match point, instead of the Frenchman.
However, with the court at his mercy, Nadal fired the forehand into the net, giving Pouille a 7-6 lead, which the 24th seed would not relinquish, hitting a winner down the line to seal victory.
"(The forehand miss) was a big mistake, yeah," Nadal admitted. "But you are 6-all in the tiebreak. I played the right point. I put me in a position to have the winner and I had the mistake. That's it.
"You cannot go crazy thinking about these kinds of things, no? You have a mistake. The opponent played a good point in the match point, and that's it. The problem is arrive to 6-All on the tiebreak of the fifth. I should be winning before. When you have 4-3, 30-Love, when you are there, is 50%. This time again, it is not on my side."
Pouille became the third Frenchman to move into the quarterfinals of the US Open 2016, with Jo-Wilfried Tsonga and Gael Monfils also sealing their places in the last eight.
Tsonga was given a bit of a workout by American Jack Sock, but always seemed to have the match under control in a 6-3, 6-3, 6-7 (7-9), 6-2 win. Monfils made his match against Marcos Baghdatis look a lot easier, cruising to a 6-3, 6-2, 6-3 win.
In the final match of the day, Novak Djokovic shrugged aside any doubts over his fitness or ring-rustiness in an accomplished 6-2, 6-1, 6-4 win over Britain's Kyle Edmund. Djokovic was given a walkover in the second round and only had to play six games in the third before Mikhail Youzhny retired, but the world number one showed he is better for the extra rest in a comfortable victory.
The defending champion will now face Tsonga in the quarterfinals, while Monfils plays Nadal's conqueror Pouille.
The women's singles matches had a couple of interesting results as well. While No.2 seed Angelique Kerber proved to be too strong for Petra Kvitova, seeded 14, with the German winning 6-3, 7-5, two unseeded players â€“ Caroline Wozniacki and Anastasija Sevastova â€“ continued their journey in New York.
Wozniacki's 6-3, 6-4 win over Madison Keys, the number eight seed, might not be that big an upset, but the manner in which Sevastova eased past 13th seed Johanna Konta 6-4, 7-5 was pretty impressive.
Joining them in the quarterfinals is last year's finalist Roberta Vinci, who beat Lesia Tsurenko 7-6 (7-5), 6-2.
It was not a day to remember for India's Sania Mirza, after the best women's doubles player in the world saw her mixed doubles challenge come to an end when she and her partner Ivan Dodig, the No.1 seeds, were beaten by the unseeded Barbora Krejcikova and Marin Draganja 6-3, 6-4.