How to watch: The Tennis Channel, 7-9 p.m. Eastern; ESPN, 9 p.m.; streaming on ESPN+ and ESPN3, 9 p.m.
Rafael Nadal vs. Dominic Thiem
Rafael Nadal, the world No. 1, won his first Grand Slam tournament at the French Open in 2005. Fifteen years later, he has continued to improve his game and learn. After a loss to Novak Djokovic in the ATP Cup this month, Nadal adjusted his game by playing more aggressively, using short, angled balls to pull his opponents into wider positions. On his way to the quarterfinals, he has dropped only one set. In his last two matches, he hit 35 more winners than unforced errors against Pablo Carreño Busta and 37 more against Nick Kyrgios.
His quarterfinal opponent, Dominic Thiem, is often compared to Nadal. Thiem, the fifth seed, is a clay-court specialist but lost to Nadal in the final of the French Open in 2018 and 2019. Thiem’s return of service, court movement and groundstrokes are all modeled on Nadal’s game, and in any other generation he would have been the most dominant player through the clay-court season. While some have described him as the heir to Nadal’s throne, it will be exceptionally difficult for him to overcome Nadal while he’s in scintillating form, especially on the slower hardcourts of Melbourne Park.
Simona Halep vs. Anett Kontaveit
Simona Halep, the fourth seed, has won two Grand Slam tournaments, at Roland Garros and Wimbledon, since her appearance in the Australian Open final in 2018. Halep may be the most consistent performer on tour, using her excellent return of serve and defensive shots to negate her opponents’ strengths. She glided through the field on her way to the quarterfinals without dropping a set. In her round of 16 match against Elise Mertens, the 16th seed, she won almost half of her returning points, forcing Mertens to play more aggressively, which led to 38 unforced errors. It’s a strategy that could work quite well against Halep’s quarterfinal opponent, Anett Kontaveit.
Kontaveit looked inconsistent in her first week in Melbourne. Although she steamrollered sixth-seeded Belinda Bencic in the third round in only 49 minutes, she has needed three sets to push past a pair of unseeded players. While her serve is usually her best weapon, she will be less likely to get free points off it against Halep, and will need to remain composed facing an opponent who knows how to make her hit an extra two or three balls to finish off what would otherwise be an easy point.