How to watch: 6 to 9 p.m., Eastern time on the Tennis Channel and 9 p.m. to 6 a.m. on ESPN2 in the United States; streaming on the ESPN+ and ESPN3 apps.

The quarterfinals of the Australian Open continue on Tuesday night. As Ashleigh Barty and Rafael Nadal look to continue their dominance, young challengers will try to unseat them on the way to the final.

Here are some matches to keep an eye on.

The times for individual matchups are estimates and may fluctuate based on when earlier play is completed. All times are Eastern.

Rod Laver Arena | 7 p.m. Tuesday

Ashleigh Barty vs. Karolina Muchova

Ashleigh Barty withdrew from the WTA tour in 2020 because of the coronavirus pandemic, deciding to stay in Australia to keep herself and her team safe. Critics believed that it would be nearly impossible for Barty, the No. 1 seed, to meet expectations, but she has been in scintillating form. She has not lost a match in the past two weeks, winning the Yarra Valley Classic and not dropping a set on her way to the Australian Open quarterfinals.

Karolina Muchova has reached the quarterfinals after two exceptional performances against Karolina Pliskova and Elise Mertens, the sixth and 18th seeds. The 24-year-old may have won both matches in straight sets, but she needed to win seven games in each to complete her upsets. Now, up against the consistent Barty, Muchova will need to temper high unforced error counts if she’s to reach her first Grand Slam semifinal.

Rod Laver Arena | 9 p.m. Tuesday

Jennifer Brady vs. Jessica Pegula

After Jessica Pegula upset the No. 5 seed Elina Svitolina, she turned to the camera and finished off her signed message with, “See you in the next round Jen B.” Jennifer Brady returned the love after her victory over Donna Vekic, writing, “Bring it Jess.” The two Americans are good friends and have been supportive of each other’s progress.

Before this tournament, Pegula had never reached the round of 16 at a major event. With wins over two top-20 players her run to the quarterfinals has been impressive with only one set dropped. Her aggressive style is well suited to the faster courts at this year’s Australian Open.

Brady, who reached the semifinals at the United States Open in September, was the only female player placed in a more restrictive quarantine after arriving in Melbourne to reach the second week. On average, Brady has lost fewer than five games per match on her way to the quarterfinals, and it’s hard to see how Pegula might be able to upset the 22nd seed.

Rod Laver Arena | 11 p.m. Tuesday

Andrey Rublev vs. Daniil Medvedev

Andrey Rublev and Daniil Medvedev secured the ATP Cup for Russia earlier this month, with neither player losing a singles match throughout. In their three meetings on the ATP Tour, Medvedev has come out on top each time, including in the quarterfinals of the U.S. Open in September.

This may be Rublev’s chance to finally overcome his friendly rival. He has looked particularly dominant, not dropping a set throughout the tournament. His match against Casper Ruud ended after only two sets when the Norwegian withdrew with an injury. Going into the quarterfinals, Rublev has led the field in both percentage of first service points won and second service points won, a sign of how hard it has been for opponents to break his serve.

Medvedev has also been playing well, aside from a chaotic, disorganized third round match against Filip Krajinovic. He has now won 18 matches in a row, with his last loss coming in October at a tournament in Vienna. Although the fast surface fits Medvedev’s flat baseline shots, Rublev’s open stance is well suited in defense, and we’re sure to see many dynamic, aggressive points.

Rod Laver Arena | 3:30 a.m. Wednesday

Rafael Nadal vs. Stefanos Tsitsipas

Rafael Nadal, the No. 2 seed, has moved smoothly through the first four rounds, no surprise for a player with 20 Grand Slam titles. Although Nadal won his only Australian Open title over a decade ago, he has reached the finals on four other occasions since, and is a clear favorite in his half of the draw to do so again. Nadal’s powerful topspin shots are well-suited to clay courts where he can drag opponents around with tightly angled shots. Nadal’s ability to exploit his opponent’s weaknesses with relentless pressure can break most players on their best days.

Stefanos Tsitsipas, the ATP finals winner in 2019, is a study in unpredictability. The fifth seed has a capable all-court game, but lacks the consistency to execute match after match. The 22-year-old has worked to improve this aspect of his game, but needed five sets to push back unseeded Thanasi Kokkinakis in the second round. After receiving a walkover in the round of 16, Tsitsipas will be well rested and hoping for an advantage against one of the most mentally tough players on tour.