Two-time Grand Slam winner Svetlana Kuznetsova upset Danish 10th seed and ex-world number one Caroline Wozniacki in a tense three-set battle to make the Australian Open last eight on Monday.
The experienced Russian won 6-2, 2-6, 7-5 and will meet top seed Victoria Azarenka.
It was a courageous win by Kuznetsova, who at 75 is the lowest ranked player left in the tournament after an injury to her right knee forced her to miss a big chunk of 2012, spending two months on crutches.
The injury meant she missed all post-Wimbledon events last year including the US Open, which ended her streak of 40 straight Grand Slam appearances dating back to 2002 at Flushing Meadow.
But Kuznetsova, who won the 2004 US Open and 2009 French Open, said she was feeling fresh again and delighted to be in the quarter-finals.
"I'm really happy with the result because in the second set I got stuck a bit," she said. "But I came out fighting in the third, and it's great.
"After 10 years of travelling I was getting tired," she added of her time on tour. "But I'm feeling fresh again and very happy to be in the quarter-finals because I struggled last year."
It was Wozniacki struggling on Monday. Her preparations for Melbourne were hurt by going out early at both the Brisbane and Sydney International tournaments, and her lacklustre form continued in Melbourne.
It was Kuznetsova who knocked her out of Sydney in the second round and while both players held their opening serves, the Russian put the Dane under pressure with some aggressive groundstrokes in the third game.
She won a crucial advantage on the second break point to go 2-1 ahead and consolidated the break by holding serve.
Kuznetsova kept pressing and got a second break in the seventh game when Wozniacki smashed a forehand into the net. She served out for the set but against the run of play, Wozniacki broke for a 2-0 lead in the second set.
The Russian lost her momentum and the Dane pushed on to get another break and take the set in 33 minutes.
It set up a tense decider and the Russian came out refreshed, taking a break for 2-1 with Wozniacki's frustration clear as she slammed her racquet to the ground.
The Dane dug deep to immediately break back as Kuznetsova lashed a forehand wide. The set became a battle with each player desperately trying to outsmart the other.
Kutznetsova finally got the breakthrough when Wozniacki netted a forehand on her serve to hand the Russian a 5-4 lead and she served out for the match.