NEW YORK (AP) — The fourth round of the U.S. Open wraps up Monday, with Carlos Alcaraz, Aryana Sabalenka and Daniil Medvedev all in action.

Alcaraz has seemed almost unstoppable so far in his title defense at Flushing Meadows, and 61st-ranked Italian Matteo Arnaldi will be the next to face that challenge in an afternoon match with a spot in the quarterfinals on the line.

Sabalenka, the No. 2 seed from Belarus who won the Australian Open in January and can overtake Iga Swiatek at No. 1 in the WTA rankings depending on their U.S. Open results, faces 13th-seeded Daria Kasatkina. And Medvedev, the third-seeded man, goes up against No. 13 Alex de Minaur.

Also on the Labor Day schedule: an all-American matchup between No. 3 Jessica Pegula and 2017 U. S. Open runner-up Madison Keys.

— In the U.S.: ESPN

— Other countries are listed here.

— Monday: Fourth Round (Women and Men)

— Tuesday-Wednesday: Quarterfinals (Women and Men)

— Thursday: Women’s Semifinals

— Friday: Men’s Semifinals

— Sept. 9: Women’s Final

— Sept. 10: Men’s Final

Play on most courts begins at 11 a.m. EDT. That includes No. 9 Marketa Vondrousova in Louis Amstrong Stadium against American Peyton Stearns. The first match in Arthur Ashe Stadium is at noon, with Pegula against Keys, followed by Alcaraz against Arnaldi. Other dayside matches in Armstrong include No. 8 Andrey Rublev of Russia against Jack Draper of Britain, and 2022 runner-up Ons Jabeur of Tunisia against Qinwen Zheng of China. Medvedev and de Minaur will start sometime after 4 p.m. Sabalenka and Kasatkina begin the night session in Ashe at 7 p.m., followed by Jannik Sinner against Alexander Zverev.

Defending champion Iga Swiatek lost in the fourth round to Jelena Ostapenko 3-6, 6-3, 6-1 on Sunday night. That means Swiatek will also lose the No. 1 ranking next week — current No. 2 Aryna Sabalenka will take over the stop spot for the first time. The result means that Ostapenko, not Swiatek, will take on Coco Gauff, a 19-year-old from Florida, in the quarterfinals Gauff became the youngest American to reach consecutive quarterfinals in New York since Serena Williams. Gauff beat Caroline Wozniacki 6-3, 3-6, 6-1. No. 10 Karolina Muchova beat Wang Xinyu 6-3, 5-7, 6-1 to reach her first U.S. Open quarterfinal and next meets No. 30 Sorana Cirstea, a 6-3, 6-3 winner over Belinda Bencic. Three American men got to the quarterfinals, the country’s largest group in that round at Flushing Meadows in 18 years. No. 9 Taylor Fritz, No. 10 Frances Tiafoe and unseeded Ben Shelton advanced with wins Sunday. Tiafoe will meet Shelton for a semifinal berth, while Fritz goes up against 23-time major champion Novak Djokovic on Tuesday.

Alcaraz is a solid favorite to beat Arnaldi, according to FanDuel Sportsbook, with the Spaniard listed at minus-4500 to plus-1600 for the Italian. Rublev, at minus-280, is favored against Draper, at plus 225. Medvedev, at minus-250, is favored to beat de Minaur at plus-202. Sinner is favored to beat Zverev, with the Italian at minus-160 to the German’s plus-132. On the women’s side, Sabelenka, at minus-315, is favored over Kasatkina’s plus-250. And Pegula, at minus-184, is favored to beat Keys, at plus-152.

What to read about the U.S. Open:

— US Open players differ on how to approach the stress of a match point. Swing away or stay safe?

— The US Open now lets coaches talk to players. The players are yelling back

— ‘ Like Snoop Dogg’s living room’: Smell of pot wafts over notorious U.S. Open court

— The US Open is the noisiest Grand Slam tournament thanks to planes, trains, music and, yes, fans

— In its initial use, new US Open video review system fails when chair umpire’s tablet malfunctions

Try your hand at the AP’s U.S. Open quiz.

149 mph (240 kph) — Speed of the fastest serves of the tournament, both hit by American Ben Shelton in his victory over countryman Tommy Paul.

14 — Number of years between Grand Slam quarterfinals appearances for 33-year-old Sorana Cirstea. She did it at the 2009 French Open before sealing her spot at this year’s U.S. Open by beating Belinda Bencic.

“Sometimes I tell them to chill a little bit because I like to think and figure out matches my own way.” —Coco Gauff, on turning to her entourage to tell them to “stop talking” from a courtside box during her victory over Caroline Wozniacki.

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AP tennis: https://apnews.com/hub/tennis