Serena Williams subdued a stubborn fightback from world number one Simona Halep to take her quest for a record-equalling 24th major into the season's first Grand Slam quarter-finals on Monday.
The 37-year-old American beat the Romanian top seed 6-1, 4-6, 6-4 in an epic three-setter to line up a last eight clash with Czech eighth seed Karolina Pliskova.
It was Williams' first match against a world number one since returning after having a baby in September 2017 and the American showed why many already regard her as the greatest of all time.
She unleashed an early onslaught and Halep was in danger crumbling before the French Open champion regrouped for a stirring comeback.
"It was an intense match and there were some incredible points," Williams said.
"She's the number one player in the world and there's a reason why... (but) I'm such a fighter, I just never give up."
Williams won her 23rd Grand Slam Down Under two years ago while two months pregnant and is the bookies' favourite to claim an eighth Australian title, despite being seeded 16th.
Another major would match Margaret Court's tally and an intensely-focused Williams had not dropped a set in three matches before meeting Halep.
Williams' started slowly when she allowed Halep to bring up three break points in the opening game, conceding with a double fault.
But the American broke back in the next, racing to the net for an overhead smash when one of her powerfully hit returns flew high off Halep's racquet.
She then ran away with the first set 6-1 in 20 minutes, blasting 10 winners to three against the world's top-ranked player.
Halep did better early in the second set, and when the American did break her in the third game she immediately broke back.
Standing well behind the baseline, she drew Williams into more rallies and began to find her range, hitting the corners to move the American around.
Halep broke again to take a set off Williams, celebrating with a fired-up double fist pump.
The turning point came in the sixth game of the third set when Halep clawed three break points but Williams held and took a decisive break in the fifth.
upbeat despite loss
World number one Simona Halep remained upbeat after a gutsy display against 23-time Grand Slam champion Williams, who is on a mission this year for a record equalling 24th title.
When asked to rate her campaign she replied: "Close to 10." "I have the courage to say that, because I took the risk to stay home so much (for off-season rest).
"I haven't prepared for the highest level in tennis, but I didn't play bad, so I'm happy about the way that it's been going this tournament. I take only the positives. I had great matches." Halep was not concerned her fourth-round exit could cost her the number one ranking, saying she preferred to concentrate on tournament results.
"The main goal is just to play as good as I can every match, to win every match I play, so the ranking doesn't really matter," she said.
"At this stage I have to work hard to get the level back, to feel 100 percent every match. So I'll work for that."
As for her immediate plans, Halep said she would be resting up and closely watching the rest of the season-opening Grand Slam.
"I'll just go home, I will rest and I will watch tennis," she said. "I'm also curious about who is going to win."