Rublev, a 21-year-old Russian ranked 43rd, has had some big wins of late, defeating Roger Federer in Cincinnati and upsetting eighth-seeded Stefanos Tsitsipas in the first round of the Open. Rublev, much like Kyrgios, is a powerful baseline player, especially on the forehand side. Both players are known to play aggressive tennis at times and to get into mental slumps after errors.

ARMSTRONG STADIUM, 11 a.m.

Taylor Townsend vs. Sorana Cirstea

Townsend pulled out a stunning upset on Thursday over fourth-seeded Simona Halep, the reigning Wimbledon champion. Townsend pressured Halep by coming to net an astounding 106 times and sticking to her plan even as Halep periodically picked out clever passing shots. Cirstea, who was ranked as high as No. 21, is known for erratic baseline play. She tends to go for winners early in a point, which can lead to as many unforced errors as it does winners. If Townsend can pressure her to go for the big shots by coming into net as frequently as she did against Halep, her winning formula may repeat itself.

GRANDSTAND, 11 a.m.

Kristie Ahn vs. Jelena Ostapenko

Ahn, 27, made it out of the first round at a major for the first time, after many years on the lower tours, trying to break into the top 200. If she wins Saturday, she will finally break into the top 100. Ostapenko, a former French Open champion and top-5 player, has struggled to recapture her top form since a wrist injury toward the end of last year. She had not won a match at Grand Slam event this year before the U.S. Open, but she has won her first two rounds in straight sets.

ASHE STADIUM, noon

Caroline Wozniacki vs. Bianca Andreescu

Wozniacki, a former world No. 1. and the 2018 Australian Open champion, has needed three sets in each round to edge past Wang Yafan and Danielle Collins. Standing in her way Saturday is Andreescu, 19, one of the most exciting young players on tour. Although she needed to withdraw from the French Open because a recurring shoulder injury, she returned to the tour in early August for the Rogers Cup in her hometown, Toronto, and won. Andreescu’s shot making variety has set her apart from many youngsters on the tour, and her hardcourt titles at Toronto and Indian Wells, where the surfaces are similar to the courts in Flushing Meadows, make her a contender. At No. 15, she is the highest seed left in her quarter of the draw.