MELBOURNE, Australia - No.30 seed Anastasia Pavlyuchenkova kicked off Day 6 of the 2020 Australian Open with the shock of the day, upsetting No.2 seed Karolina Pliskova, 7-6(4), 7-6(3) to surge into the second week.

The former World No.13 saved two set points late in the second set and saved her best tennis for the pair of Sudden Deaths to advance after two hours and 25 minutes on Rod Laver Arena.

Pavlyuchenkova had never beaten the former World No.1 in six previous meetings, though their last encounter was the first to go three sets at the 2018 Nature Valley International. The Russian has played some of her best tennis at the Happy Slam, reaching the quarterfinals in two of the last three years and narrowly losing to Danielle Collins in the last eight 12 months ago.

"I am really happy, it was a lot of fun," said Pavlyuchenkova in her on-court interview. "I really enjoyed it and even had goosebumps after some points. To get a win and beat Karolina for the first time was amazing."

A semifinalist in Melbourne last year, Pliskova was yet to drop at set this fortnight and came into the match on a six match winning streak after starting the decade with a third Brisbane International title.

The match began in most unusual fashion as the self-styled Ace Queen was made to battle through a 30-point opening service game, one that lasted 12 deuces and forced her to save six break points. While Pavlyuchenkova didn't win that battle, she proved game for more as she took a 4-1 lead.

Pliskova responded in kind, leveling the set and pushing the No.30 seed into another long service game, only this time it was Pavlyuchenkova who saved five break points through six deuces to emerge on top.

From a mini-break down in the ensuing tie-break, Pavlyuchenkova won four straight points and never relinquished her lead, clinching the set as the 2016 US Open finalist netted a mid-court forehand.

Pavlyuchenkova kept up her momentum early in the second set, breaking to open and holding on for a 3-1 lead. With a double break deficit looking possible, Pliskova replied with a running backhand down the line and leveled the set in the very next game.

Yet another marathon game played out on the Pliskova serve at five games apiece, with the Czech star saving four more break points through nine more deuces. A rare hiccup from Pavlyuchenkova saw her put down three double faults and give Pliskova two looks at leveling the match, both of which the Russian saved with winners.

A fifth ace sent the match to its second tie-break, which she proceeded to dominate to book her spot in the second week.

Power won the day for Pavlyuchenkova, who struck a whopping 51 winners while only hitting 43 unforced errors, an impressive ratio for a player going for that much off the ground. Pliskova maintained a positive differential as well, striking 35 winners to 29 unforced errors, but managed just six aces and couldn't take advantage of her rival's sometimes-inconsistent serve.

"My goal was to return well today, she is the ace queen on tour," added Pavlyuchenkova. "I thought that if I took at least one or two games on her serve, it would be amazing and I also held my serve which helps. It was a good match for me today."

Standing between Pavlyuchenkova and a third Australian Open quarterfinal is 2016 champion Angelique Kerber, who withstood a barrage of big hitting from Italian powerhouse Camila Giorgi on Margaret Court Arena.

"I think she was playing very well today," said Pliskova. "Maybe the best that she has played against me so far in the last couple matches. But let's say I was about 40% today of my game so, of course, then she can feel so much better if I just don't play enough what I can play.

"But, yeah, that's how it is. I think especially the important moments she always served well so I had couple chances here and there. First and second set of course some set points. But I think she just played better than me."

2020 Australian Open Highlights: Pavlyuchenkova powers to Pliskova stunner