I could sense it coming, and--unfortunately--it did: Petra Kvitova, who has been on fire at this U.S. Open, put up a half-spirited resistance against round of 16 opponent Jessie Pegula in today's first match, allowing Pegula to easily defeat her, 6-3, 6-2. The Czech player served well, but she made twice as many unforced errors as Pegula, who broke her six times. This "should" have been a tightly contested, entertaining match, but almost from the moment she stepped onto the court, the Czech star looked depleted. We have seen this pattern over and over with Kvitova, and it's very unfortunate.
This is to take nothing away from Pegula, who is staying calm and playing at a consistently high level.
World number 1 Iga Swiatek had her hands full in the first set of her match against Jule Niemeier, whose quarterfinal match at Wimbledon was, in my opinion, the finest match played at that event. But Swiatek, as she so often does, solved the problem, and returned to win the next two sets, posting a 2-6, 6-4, 6-0.
Vika Azarenka served for the first set at 5-4 in her round of 16 match against 2016 runner-up Karolina Pliskova, but she was broken (in the final point, she broke herself by double-faulting), and Pliskova went on to take that set 7-5. Again, Azarenka took the lead in the second set, again, Pliskova caught up, but eventually lost the set in a tiebreak. Nevertheless, she prevailed, 7-5, 6-7, 6-2.
The final round of 16 match was played between Danielle Collins and Aryna Sabalenka. It was notable partly because Collins could not find a first serve. It was equally notable because her abysmal service stats didn't seem to bother her; she got creative with her second serve, and she went to work on Sabalenka's serve. The degree of mental energy that Collins preserved by just accepting that she was having a bad serving night and getting on with things was likely quite high.
Collins took the first set. In the grueling seventh game of the second set, Sabalenka saved seven game points, and then had treatment for her left thigh. Her serve intact, she went on to win the second set, after which she received some sort of leg treatment. But something else had happened, too: It was as if someone had pulled a plug and let all the air out of Collins. She had practically been willing herself to win points, and suddenly, she was just a good player without much of a serve who was being dominated by a steam-rolling opponent.
When Sabalenka served at 4-1 in the third set and was broken, it looked like Collins might come back to life, but she was broken back in the next game, and Sabalenka proceeded to successfully serve for the match. Her 3-6, 6-3, 6-2 victory was hard-won, despite her opponent's issues. Between them, the players hit 72 winners and made 63 unforced errors, including 20 double faults.
Here is the quarterfinal draw:
Iga Swiatek (1) vs. Jessie Pegula (8)
Karolina Pliskova (22) vs. Aryna Sabalenka (6)
Coco Gauff (12) vs. Caroline Garcia (17)
Ons Jabeur (5) vs. Ajla Tomljanovic
There have already been three major upsets in doubles, though one of them is more of an upset on paper than anything else. Top seeds Veronika Kudermetova and Elise Mertens were defeated in the second round by the unseeded team of Kirsten Flipkens and Sara Sorribes Tormo, and 2nd seeds Coco Gauff and Jessie Pegula went out in the first round to the unseeded team of Leylah Fernandez and Daria Saville. 4th seeds Lyudmyla Kichenok and Alona Ostapenko lost in the third round to 14th seeds Caroline Garcia and Kiki Mladenovic, but that team's seeding doesn't really reflect their level of competence.