NEW YORK — Iga Swiatek and Jannik Sinner flashed their No. 1 form on Thursday with powerful performances that moved them into the third round of the U.S. Open.

Swiatek raced past Japanese qualifier Ena Shibahara, 6-0, 6-1, finishing off the match in 65 minutes. It took the 2022 U.S. Open champion longer than that to play the second set of her first-round match, when she needed a tiebreaker that she eventually closed out in 72 minutes.

“I just felt the rhythm was much better,” Swiatek said. “I was a bit tense in my last match, so today I just wanted to focus on the right things.”

Earlier, Sinner downed Alex Michelsen of the U.S., 6-4, 6-0, 6-2 in 1 hour, 39 minutes.

Sinner dropped the first set in his opening match in New York but didn’t encounter much trouble while facing his second straight American on Arthur Ashe Stadium. The Italian earned his 50th victory of the season, including his ATP Tour-leading 30th on hard courts.

His previous one was a little shaky after a slow start against Mackie McDonald, so Sinner got in a practice session after that match and was happy with the results Thursday.

“Trying to keep going, trying to understand what works here best on these courts. Let’s see what I can do in the next round,” he said.

That will be against Christopher O’Connell of Australia on Saturday.

Sinner beat Michelsen for the second time this month, having also won a second-round match in Cincinnati shortly before it was revealed that he tested positive twice for an anabolic steroid in March.

Another Italian, Jasmine Paolini, played just three points before advancing when former No. 1 player Karolina Pliskova appeared to injure her left foot. The No. 5-seeded Paolini, who has reached the finals of the French Open and Wimbledon in her breakout season, advanced past the second round of the U.S. Open for the first time.

“Finally, we made third round!” she said with a laugh during an interview on the court.

The score was 15-all, with Paolini serving, when Pliskova stepped awkwardly on her left foot while trying to change directions during a point she lost. That made it 30-15, and that’s where the scoreboard remained, because Pliskova headed to the sideline and asked for a visit from a trainer.

Pliskova, the runner-up at the U.S. Open in 2016 and at Wimbledon in 2021, removed both of her shoes and took off her left sock. The trainer examined her left foot and, eventually, Pliskova said she couldn’t continue competing and limped off the court at Louis Armstrong Stadium.

“It’s so sad. I hope she recovers really soon, because it’s bad to leave the court like this,” Paolini said. “I don’t know what to say, because we didn’t play a match. It’s not good for tennis.”

Paolini will next play No. 30 seed Yulia Putintseva.

Other women’s winners included No. 6 Jessica Pegula, No. 15 Anna Kalinskaya, No. 16 Liudmilla Samsonova and No. 18 Diana Shnaider. Pegula took out fellow American Sofia Kenin.

But No. 4 seed Elena Rybakina, the 2022 Wimbledon champion, withdrew before her second-round match, sending French qualifier Jessika Ponchet to the weekend.

“Unfortunately, I have to withdraw from my match today due to my injuries,” Rybakina said in a statement. “I did not want to finish the last Grand Slam of the year this way but I have to listen to my body, and I hope I can close out the remainder of the year strong.”

No. 7 seed Hurbert Hurkacz was eliminated in straight sets by Jordan Thompson, and No. 16 Sebastian Korda was knocked out by Tomas Machac.