Serena Williams battled into her 11th Australian Open quarter-final on Monday, joining sister Venus, in her unrelenting quest for a record Grand Slam title and the return of her top world ranking.
The American powerhouse was tested by Czech 16th seed Barbora Strycova but she dug deep to win 7-5, 6-4 in hot conditions and will face either Johanna Konta or Ekaterina Makarova for a place in the last four.
Williams has made clear in Melbourne she is here for one reason only — to win — and she was in a fighting, but nervy, mood during an entertaining contest.
The 35-year-old had added incentive after the shock defeat on Sunday of top seed Angelique Kerber, the woman who beat her in the final last year and then snatched her top world ranking.
Williams, seeded two, can again become world number one if she lifts the trophy this week.
"I love pressure, I deal well with pressure," she said, when asked why she keeps coming back for more.
"I love this game and I honestly have nothing to lose. Everything is a bonus for me now."
Williams winning the title on Saturday would rewrite history. She is not just chasing a seventh Melbourne crown, but also a 23rd Grand Slam to surpass Steffi Graf's Open-era record.
With her sister, a potential final opponent, already safely into the last eight in the other side of the draw, Williams had to use all her experience to get past a dogged Strycova.
Despite the temperature already past 30 Celsius (86 Fahrenheit) when they began at 11:00am, Williams opted to wear knee-length black leggings and sleeves, and she made a slow start.
It was Strycova who drew first blood, breaking the first Williams serve, but with the sweat starting to drip off her she immediately broke back with a sizzling crosscourt forehand.
But Williams' first serve was still not firing, with just 33 percent successful in the opening games, and the Czech took full advantage to break to love and go 2-1 in front.
It was woeful serving from both players with Williams broken again before they both began to warm to the task.
Williams finally held serve in the fifth game but it didn't last long when Strycova broke again to go 4-3 ahead.
Another break — an incredible sixth in eight games — put Williams level and she then held, before a defensive Strycova saved four set points in a marathon 10th game.
Williams was fired up and screaming "C'mon!" and she went 6-5 ahead before Czech, serving to stay in the set, was finally undone on the eighth set point by a lucky shot from the American that came off her racquet frame.
Strycova, at a career-high ranking of 16, is a two-time former girls champion in Melbourne but had never been past round four in the main draw.
And with her nose in front, Williams was never going to let that happen and a netted volley from the Czech gave her an early break for 2-1 in the second set.
Strycova was wilting and Williams was in control, and despite being broken when serving for the match she broke straight back to book her place in the last eight.