Melbourne: World No 1 Simona Halep and the woman who topped the rankings a year ago, Angelique Kerber, can set up a blockbuster showdown if they come through the Australian Open quarter-finals on Wednesday.
Romania's Halep was too good for Japanese youngster Naomi Osaka in a straight sets last 16 win.
But she has been nursing a painful ankle and an aching body after enduring a 3 hr 44 min thriller to beat Lauren Davis 15-13 in the third set in round three.
She faces a tough examination against former number one and sixth seed Karolina Pliskova as both go in search of a first Grand Slam title.
"Pliskova is always dangerous. She's playing great these days. I'm used to her," said Halep, who leads their head-to-head series 5-1.
The Romanian beat the Czech in three sets in their only Grand Slam encounter, on clay in the semi-final at Roland Garros last season.
"It is going to be a new match. You never know what's going to happen," Halep said as she targets a maiden semi-final at Melbourne Park, having fallen in the last eight in 2014 and 2015.
The 21st seed Kerber's clash against US Open finalist Madison Keys looks to have the makings of a classic.
Two-time Grand Slam champion Kerber has yet to face a seed. But her third-round annihilation of Maria Sharapova gave notice she is approaching the form that swept her to the title two years, stunning Serena Williams in the final.
The German is the only major winner left in the draw but 17th seed Keys has enjoyed an almost unnoticed, impressive run without dropping a set.
New ball game
The American, who is targeting a second semi-final at Melbourne, took just 68 minutes to destroy eighth seed Caroline Garcia 6-3, 6-2 in the last 16.
Meanwhile, super-fit Kerber was made to run all over the court for three highly entertaining sets by the unorthodox variety of Taiwan's Hsieh Su-wei.
Kerber acknowledged that facing Keys, who smashed 32 winners and nine aces in beating Garcia, would be a whole new ball game.
"It's a completely different match. I know what to expect. I know she's a hard hitter and has a great serve," said Kerber.
Keys said Kerber's ability to chase down lost causes would present a new problem.
"I think she has an ability to cover the court and anticipate like really no one else does," said the 22-year-old, who first reached the semi-finals in Melbourne as a teenager in 2015.
"I know she's going to make three more balls than other girls may be able to get to."
Pliskova has the least time to recover for her clash with Halep.
She took almost three hours to get past fellow Czech Barbora Strycova in a last-16 match that did not finish until just before 2:00 am on Tuesday.
But she said she would have a game plan for Halep.
"I think there is always chance to beat her. It's going to be about me. If I don't play well I don't have the chance. I have to get my mindset ready for this."
Updated Date: Jan 23, 2018 20:01 PM