Wozniacki had the top ranking for the 2011 and 2012 editions of the season's first major, but lost in semifinals two years ago and the quarterfinals last year. Her 6-2, 2-6, 7-5 defeat to two-time Grand Slam winner Kuznetsova in the Round of 16 this time follows back-to-back first-round exits at Wimbledon and the U.S. Open.
Kuznetsova is moving in the other direction, after entering the tournament at No. 75. She's on a comeback from a right knee injury that ruled her out of the last U.S. Open, ending a run of contesting 40 consecutive majors.
The 27-year-old Russian moved into a quarterfinal and will next face either No. 1-ranked Victoria Azarenka or Elena Vesnina.
Play on Day 7 ran into Day 8 overnight, when Novak Djokovic needed just over 5 hours to beat Stanislas Wawrinka 1-6, 7-5, 6-4, 6-7 (5), 12-10 in a fourth-round match Sunday night, on the same court where he needed 5:53 to beat Rafael Nadal in last year's final.
"I just had flashback of 2012," said Djokovic, who ripped off his shirt to celebrate again, like he did last year. "It was maybe 45 minutes less this match than the one 12 months ago, but still it was still as exciting. I tried to enjoy the moment and couldn't ask for more. What a match point ... unbelievable."
The win was Djokovic's 18th in a row at Melbourne Park after winning the last two Australian titles, and earned him a place in the quarterfinals of a 15th consecutive major.
Wawrinka said he would take more positives than negatives out of the match. He led 5-2 in the second set after outplaying Djokovic in the first.
"For sure, I think the best match I have ever played," Wawrinka said. "I fought like a dog like always. At 4-4 in the final set, I thought I might have won the match, but he was just better."
Djokovic will next play No. 5 Tomas Berdych, who beat South Africa's Kevin Anderson 6-3, 6-2, 7-6 (13).
Fourth-seeded David Ferrer advanced 6-2, 6-1, 6-4 over No. 16 Kei Nishikori of Japan to set up a quarterfinal against fellow Spaniard Nicolas Almagro.
Roger Federer plays Milos Raonic later Monday, and U.S. Open champion Andy Murray faces Gilles Simon.
Serena Williams, aiming for a third consecutive major title, will play her fourth-round match against No. 14 Maria Kirilenko of Russia.
They will have a tough time matching the spectacle of Sunday's late-night encounter, which also overshadowed Maria Sharapova's accomplishment.
The reigning French Open champion advanced to the quarterfinals with a 6-1, 6-0 win over Kirsten Flipkens, and has lost just five games through four rounds. That's three fewer than the previous low mark at the Australian Open, held by Steffi Graf and Monica Seles.
She next plays fellow Russian Ekaterina Makarova, who beat fifth-seeded Angelique Kerber 7-5, 6-4. Sharapova defeated Makarova in the quarterfinals here last year on her way to the final, which she lost in straight sets to Victoria Azarenka.
Li Na, who reached the final here in 2011 and won the French Open later that year, saved a set point in the tiebreaker before beating Julia Goerges 7-6 (6), 6-1. She'll play No. 4 Agnieszka Radwanska, who beat No. 13 Ana Ivanovic 6-2, 6-4 for her 13th consecutive win.