Top seed Jannik Sinner left the doping controversy that marred his US Open preparations in the rear view mirror with a largely drama-free start to his campaign while fellow title contender Carlos Alcaraz also advanced after a minor blip.
But in a stunning upset, Romanian qualifier Elena-Gabriela Ruse bounced Wimbledon champion Barbora Krejcikova from the second round of the US Open on Wednesday, beating the Czech 6-4, 7-5 to reach the third round of a Grand Slam for the first time.
Ruse, ranked 122nd in the world, pulled off the biggest upset of the tournament so far with her win over the eighth-ranked Krejcikova.
German fourth seed Alexander Zverev on Wednesday beat Frenchman Alexandre Muller 6-4 7-6(5) 6-1 to set up a third-round meeting with Tomas Etcheverry, who beat fellow countryman Francisco Cerundolo 6-3 4-6 6-4 1-6 6-3.
Frances Tiafoe of the US advanced to the third round after Kazakh Alexander Shevchenko retired in the third set with the American leading 6-4 6-1 1-0.
The 20th seed could next face compatriot Ben Shelton if he defeats Spaniard Roberto Bautista Agut.
The spotlight was firmly on Sinner in the day session as the Italian overcame a slow start to seal a 2-6 6-2 6-1 6-2 win over American Mackenzie McDonald a week after he was cleared of any wrongdoing over two failed tests in March for a banned drug.
Sinner, who has maintained his innocence, has been under intense scrutiny after escaping a doping ban but the 23-year-old was pleased to have the backing of fans on Arthur Ashe Stadium.
“The response from fans, I feel it has been great, also throughout when the news came out, in the practice sessions, there was a lot of support, which I’m very glad and happy about,” Sinner said.
“It is still a little bit, you know, not easy. You have to go day by day ... I was curious to see how the reaction of the fans has been, but it has been very positive.”
Alcaraz, another Flushing Meadows crowd favourite, gifted Australian qualifier Li Tu a set but the 2022 champion steadied the ship before closing out a 6-2 4-6 6-3 6-1 victory inside three hours.
Briton Dan Evans needed a much bigger effort to advance as he beat Russian 23rd seed Karen Khachanov 6-7(6) 7-6(2) 7-6(4) 4-6 6-4 in the longest US Open match of the professional era – an exhausting five hours and 35 minutes.
“Obviously I won’t practice tomorrow. Just recover and try and recover as best as possible. I was hurting all over really,” Evans said.
“I don’t think I’ve played five hours, that long, in a day ever in two sessions, never mind in one.”
Former champion Emma Raducanu was unable to avoid the exit door as the Briton fell 6-1 3-6 6-4 to Sofia Kenin, while fourth seed Elena Rybakina overcame a late fightback to beat Destanee Aiava 6-1 7-6(1). French Open and Wimbledon runner-up Jasmine Paolini was made to work hard by 2019 New York champion Bianca Andreescu but went through 6-7(5) 6-2 6-4.
Fifth Daniil Medvedev fought off a spirited challenge from Dusan Lajovic to win 6-3 3-6 6-3 6-1.

“I have no words”
“Oh my God! I have no words at this moment,” said a beaming Ruse after beating Krejcikova on Wednesday. “It’s just a dream for me,” she added.
The Czech, eliminated in the quarter-finals of the Paris Olympics, opted not to play any hard-court tune-ups heading into the US Open, withdrawing from Toronto with a thigh injury. She acknowledged before the tournament that obligations in the wake of her Wimbledon victory “took a lot of energy,” although adding a second major after her 2021 French Open victory had boosted her confidence and sense of calm.
The 26-year-old Ruse, who thanked her team for seeing her through a series of injuries, next faces 26th-seeded Paula Badosa of Spain, a 6-3, 7-5 winner over American Taylor Townsend.
“I don’t care, to be honest right now. I just want to enjoy,” said Ruse, who was especially pleased that her father, Adrian, was on hand to watch her play in the United States for the first time.