Nadal said he'd head to Melbourne after a brief stopover in Sydney for a Fast4 event to prepare for the Australian Open. The 32-year-old Spaniard is hoping he can still win the season's first major, which starts on Jan. 14, despite his lack of match preparation.

Doctors "say that it's a very small thing, but can become a big thing," Nadal said during a news conference staged while Murray was playing Medvedev on Pat Rafter Arena. "When you increase the intensity on the muscle competing, then there is a big risk to make something bigger." Also exiting the men's draw on Wednesday where defending champion Nick Kyrgios, who lost to Jeremy Chardy 6-7 (5), 6-2, 6-3, and third-seeded Kyle Edmund, who lost to Japanese qualifier Yasutaka Uchiyama 7-6 (6), 6-4.

Second-seeded Kei Nishikori beat and 2017 champion Grigor Dimitrov had straight-set wins earlier to set up a quarterfinal showdown — a rematch of their final in 2017. Also advancing were fifth-seeded Milos Raonic and seventh-seeded Alex De Minaur.

Anett Kontaveit beat fourth-seeded Petra Kvitova 7-5, 7-6 (1) to reach the women's quarterfinals, and Anastasija Sevastova advanced to a quarterfinal match against U.S. Open champion Naomi Osaka.

Fifth-seeded Karolina Pliskova had a 7-5, 6-2 win over Marie Bouzkova and will next meet Ajla Tomljanovic, who beat Johanna Konta 6-2, 7-6 (2). Donna Vekic ousted No. 6 Kiki Bertens 7-6 (5), 1-6, 7-5 and will take on Sasnovich in the quarterfinals.

The absence of Nadal, who was replaced in the draw by Taro Daniel, and Murray puts more focus on the Nishikori-Dimitrov quarterfinal match. Nishikori opened his year with a 7-5, 6-2 win over Denis Kudla.

The sixth-seeded Dimitrov, who beat Nishikori in the 2017 final here, had to withstand a late comeback from John Millman before winning 6-3, 6-4. He's using the quarterfinal match as a barometer for where his preparations stand for the Australian Open.

"It's great. I mean it's right off the blocks," Dimitrov said. "It's perfect to play a match like that to kind of see where your game is at."

AP