US Open 2018 Highlights: Williams vs. Williams Match Is On

• Serena Williams and Venus Williams won on Wednesday at the 2018 U.S. Open to set up a match between the sisters in the third round.

• Rafael Nadal cruised into the third round, but Andy Murray, in his first Grand Slam tournament in more than a year, was eliminated.

• The U.S. Open changed its policy for where a woman can change her clothes during a match.

• Scores and schedules: Men | Women

• Read highlights from Day 2 here.

Serena Williams powered her way past Carina Witthöft, 6-2, 6-2. Michelle V. Agins/The New York Times

Here’s what happened on Day 3 of the U.S. Open:

Muguruza Takes a Late-Night Loss

Garbiñe Muguruza’s struggles continued with a 3-6, 6-4, 6-4 loss to the qualifier Karolina Muchova, which ended after 1 a.m. The 12th-seeded Muguruza has won only three matches since reaching the semifinals of the French Open. As the defending champion at Wimbledon, she lost in the second round. She also withdrew from two hardcourt tournaments with an arm injury.

Muchova, 22, is ranked 202nd and is playing in the main draw of a Grand Slam event for the first time.

Confusion About the Heat Policy

With the temperature in the mid-90s for the second day in a row, the men again played under a new extreme heat policy, which calls for a 10-minute break between the third and fourth sets.

On Tuesday, the first day the policy was used, five men retired from matches with heat-related problems. But on Wednesday, the only man who retired from a match, Jason Kubler, did so because of an ankle injury.

The policy has created relief — and confusion. It allows for players to “go anywhere” for a respite from the heat, but prohibits coaching and off-court medical treatment. Andy Murray said he saw at least one violation of that protocol during his second-round loss to Fernando Verdasco on Wednesday.

Murray said that when he came out of the shower in the locker room during the break, he saw Verdasco speaking with his coach and another Spanish player. Murray said he alerted an official.

After returning to the court before the start of the fourth set, Murray expressed his frustration about people not knowing the rules to the chair umpire. Verdasco was not penalized.

“This is one of the biggest events in the world,” Murray said. “If you have rules like that, you need to stick with them because one player getting to speak to the coach and the other not is not fair.”

Verdasco denied that he had talked with his coach during the break — though he acknowledged that his coach was in the locker room.

“I think he went to the toilet,” Verdasco said. “I obviously cannot say, ‘Don’t go to the toilet.’ But actually, we didn’t even speak one word.”

Verdasco said that he took an ice bath and talked to Marcos Baghdatis and Baghdatis’s coach, who were in the room, but that he never made contact with anybody from his own team.

“I don’t want to say that he lie,” Verdasco said, referring to Murray. But, Verdasco added, “I know exactly the rule and I don’t want to be the one breaking it.”

Hours later, Murray posted a caustic statement on Instagram: “I’m off to get a health check as apparently I’ve started imagining things #liarliarpantsonfire”

SCOTT CACCIOLA

Nadal Rolls On

Top-ranked Rafael Nadal hasn’t had much trouble through two rounds at the U.S. Open. David Ferrer retired in the second set of their first-round match, and Wednesday night Nadal dispatched Vasek Pospisil, 6-3, 6-4, 6-2, in two hours. Nadal will next face No. 27 seed Karen Khachanov.

It Will Be Williams vs. Williams

Several hours after Venus Williams advanced to the third round, her sister Serena did the same, defeating Carina Witthöft, 6-2, 6-2, to set up a third-round clash between the sisters.

They have played each other 29 times in their decorated careers, with Serena winning 17 of their matches. Venus won the last match between them, in the third round of the BNP Paribas Open in Indian Wells, Calif. That was Serena’s first tour event after returning from her maternity leave.

“It’s definitely a tough draw,” said Venus Williams, who quickly got annoyed at her post-match news conference with a series of questions about her sister. “You’re beating it up now. Any other questions about anything else?”

Isner Escapes in 5 Sets

John Isner has so much experience in five-set matches that it is hard to count him out when a match goes long. Put him in an intimate Grandstand Stadium and surround him with a raucous pro-American crowd, and, well, good luck, Nicolas Jarry.

“This right here is what the U.S. Open is all about,” Isner said.

Isner, the No. 11 seed experiencing his finest season at age 33, avoid a second-round upset with a 6-7 (9), 6-4, 3-6, 7-6 (2), 6-4 win over Jarry.

Isner had 38 aces among his 72 winners. Jarry, who like Isner can hit 130 m.p.h. serves, had 61 winners, including 21 aces. The average rally length in the match was a paltry 2.38 shots.

Amid all that firepower, it was a lob winner that gave Isner the crucial break with Jarry serving at 4-4 in the fifth.

Murray’s Comeback Stalls

In many ways, Andy Murray resembled his old self in his second-round match against No. 31 seed Fernando Verdasco. Murray screamed at himself — a lot. He bickered with the chair umpire. He tossed his racket in frustration. Parts of his game looked familiar, too, like his punishing ground strokes and his desire to win.

But about eight months removed from hip surgery, Murray has found his comeback to be halting, full of peaks and valleys, and Verdasco wore him down in a 7-5, 2-6, 6-4, 6-4 victory at Arthur Ashe Stadium.

Murray, a former world No. 1 and three-time Grand Slam champion, entered the Open ranked 382nd and was unseeded after playing sparingly this year. He had won eight straight matches against Verdasco dating to 2009. But Murray was playing his first tournament with a best-of-five-set format since returning in June.

“It’s still quite early in the process for me,” he said. “I did all right. I chased balls down right to the end of the match. I wasn’t giving up on points. It wasn’t the most comfortable I felt on a tennis court. But I got through it and fought right to the end.”

Verdasco will next play third-seeded Juan Martin del Potro, who dominated Denis Kudla, 6-3, 6-1, 7-6 (4). In breezing through the first two rounds, del Potro has spent a total of 3 hours 39 minutes on court. Verdasco’s win over Murray alone took 3:23. SCOTT CACCIOLA

A First for Fritz

The story lines of the match between Taylor Fritz and Jason Kubler on Court 13 were probably a mystery to all but the most passionate tennis fans.

Both were ranked No. 1 as juniors, Kubler in 2010 and Fritz in 2015. Both were trying to reach the third round of a Grand Slam event for the first time.

It was Fritz who made it through, after Kubler sustained an ankle injury late in the third set and was forced to retire after two points in the fourth, with Fritz leading by 6-3, 3-6, 6-3.

That was an unfortunate and all too common end for Kubler, a 25-year-old Australian. Before this year, he hadn’t played in a major tournament since 2010. He played exclusively on clay courts for more than three years, until May 2015, because of a series of knee injuries.

Playing primarily on the Challenger tour, a rung below the ATP Tour, Kubler, 25, has had a strong summer on hard courts, winning two titles. His first-round win over Roberto Bautista Agut was Kubler’s first victory in the main draw of a major.

Asked if he was elated to get to the third round of a major, Fritz said: “Not as happy as I would be if I, you know, finished the match and won it without my opponent retiring. I mean, I hope he feels better. I saw it. After I came in, I saw the video of what happened. It looked really bad.”

On Friday, Fritz will play ninth-seeded Dominic Thiem, who needed five sets to get past the American Steve Johnson, 6-7 (5), 6-3, 5-7, 6-4, 6-1.

Venus Wins. Will Serena Follow?

Venus Williams did her part in making a Williams sisters third-round match happen. She defeated Camila Giorgi, 6-4, 7-5, at Louis Armstrong Stadium.

Williams rallied from a break down in the second set to close out Giorgi, the 40th-ranked Italian who has 24 career wins over top-20 players.

Serena Williams faces Carina Witthoeft on Wednesday night to try to claim her spot in the third round.

Stephens Survives Marathon

Sloane Stephens, the defending champion, was pushed for 2 hours 46 minutes on a brutally hot day but escaped with a 4-6, 7-5, 6-2 victory over the Ukrainian qualifier Anhelina Kalinina.

Stephens, the No. 3 seed, particularly struggled with her serve. She faced 20 break points in the match and was broken five times.

Her victory set up a marquee third-round match against Victoria Azarenka, a two-time U.S. Open finalist.

Wawrinka Moves On

Stan Wawrinka is in the third round of a Grand Slam event for the first time since he was the runner-up at the 2017 French Open. He struggled with a knee injury soon after and has been working his way back to top form this year.

On Wednesday, he defeated the French qualifier Ugo Humbert, 7-6 (5), 4-6, 6-3, 7-5.

Wawrinka, the 2016 U.S. Open champion, will next play No. 25 seed Milos Raonic, who defeated Gilles Simon, 6-3, 6-4, 6-4.

Tsitsipas Tumbles Out

Stefanos Tsitsipas, a 20-year-old from Greece, was one of the hottest players on the ATP Tour this summer after runs to the semifinals in Washington and to the final in Toronto, where he beat four top-10 players. He has surged to a career-high ranking of No. 15.

But he stalled at the U.S. Open on Wednesday, losing in the second round to another rising young player, 22-year-old Daniil Medvedev of Russia, 6-4, 6-3, 4-6, 6-3.

Perhaps that means he will have more time to add a video about his travels around New York to his YouTube channel.

Azarenka Is Back in Familiar Territory

With an efficient 6-1, 6-2 win over No. 25 seed Daria Gavrilova, Victoria Azarenka advanced to the third round of a major for the first time since Wimbledon last year.

A tremendous hardcourt player, Azarenka, 29, has had quite a bit of success at the U.S. Open over the years, including two runner-up finishes and a junior championship. But she had not played in Flushing Meadows since 2015. She gave birth to her son, Leo, in 2016, and then missed last year’s tournament because of a child custody issue. Despite recently raising her ranking to No. 79, Azarenka needed a wild card to gain entry into the Open.

In other women’s matches, No. 7 seed Elina Svitolina, No. 15 Elise Mertens, No. 19 Anastasija Sevastova and No. 23. Barbora Strycova also reached the third round.

U.S.T.A. Changes Course on Changing Shirts

After taking a break from the blistering heat on Tuesday, Alizé Cornet came back onto court with her top on incorrectly. When she tried to turn it around, she revealed a problematic policy.

Cornet was assessed a code violation for unsportsmanlike conduct for taking her shirt off behind the baseline before the game began. She was wearing a sports bra under her top, and the change took only a few seconds. She had been warned that such a violation was possible.

Cornet( info - @nicklester , @BenRothenberg,@ymanojkumar)(Eurosport) pic.twitter.com/RlfQT3t77a
— doublefault28 (@doublefault28) Aug. 28, 2018

On Tuesday evening, the U.S.T.A. said that there was a “longstanding policy” restricting women from removing their tops on court, and that the code violation was correctly assessed.

No such rule has existed for men, who change their shirts several times on court during a match. Rafael Nadal, the three-time U.S. Open champion, takes off his shirt and stands around shirtless for a few minutes after each match he wins. There have been few complaints.

By Wednesday morning, after an outcry on social media, the U.S.T.A. had issued a new statement regarding changing clothes.

“All players can change their shirts when sitting in the player chair,” the U.S.T.A. said. “This is not considered a Code Violation.

“We regret that a Code Violation was assessed to Ms. Cornet yesterday. We have clarified the policy to ensure this will not happen moving forward. Fortunately, she was only assessed a warning with no further penalty or fine.”

Female players, the U.S.T.A. added, were also able to change their tops in a more private location near the court if they wished.

The WTA Tour expressed relief at the adjustment, calling the previous policy “unfair” and not in keeping with its own rules.

“We are pleased to see the U.S.T.A. has now changed this policy,” the WTA said. “Alizé did nothing wrong.” BEN ROTHENBERG

Extreme Heat Policy in Effect

The U.S. Open instituted a new extreme heat policy that applies to men and women on Tuesday, and said Wednesday it would continue until further notice. In women’s singles, the players will be allowed a 10-minute break between the second and third sets. In men’s singles, players will be allowed a 10-minute break between the third and fourth sets.