Japanese US Open champion Naomi Osaka and sixth seed Elina Svitolina survived big scares but displayed fighting qualities to pull back from the brink at the Australian Open on Saturday.

On day six at Melbourne Park, fourth seeded Osaka looked down and out against Taiwanese veteran Hsieh Su-wei before battling back to win 7-5, 4-6, 6-1 and set up a last 16 meeting with Latvia’s Anastasija Sevastova, who beat China’s Wang Qiang in straight sets.

Pliskova struggled with a painful shoulder complaint that required treatment at every change of ends, and medical timeouts, before somehow beating China’s Zhang Shuai 4-6, 6-4, 7-5 as the temperature rose in the centre court sunshine.

They played ahead of Serena Williams making another bow on Rod Laver Arena as she gathers steam in her bid to win a record-equalling 24th Grand Slam title.

The American great takes on unseeded Ukrainian teenager Dayana Yastremska.

Misfiring world number one Simona Halep is also in action, testing herself against Williams’ sister Venus on Margaret Court Arena with the winner potentially facing Serena for a berth in the quarter-finals.

Osaka’s win equals the 21-year-old’s best performance at the Australian Open, where she reached the last 16 in 2018 but lost to Halep.

But she looked headed for the exit when she conceded the first set and was down 4-1 in the second before winning five straight games to force a decider.

“I just didn’t want to give up,” said the Japanese, who made 42 unforced errors and received a code violation after throwing her racquet.

“I really love Grand Slams so I did anything I could do to stay here a bit longer.”

Ukrainian Svitolina also staged an epic fightback and shrugged off an injury scare to reach the fourth round.