Melbourne - Top seed Serena Williams again left it late before storming into the Australian Open quarter-finals Monday, as sister Venus returned to the big time and Dominika Cibulkova crashed Victoria Azarenka's comeback party.
American teenager Madison Keys, mentored by Venus' old sparring partner Lindsay Davenport, also earned a spot in the women's last eight, the latest of the so-called new generation to knock on the door of Grand Slam success.
Keys will meet Venus, a player 15 years her senior, in the quarters, while Serena lines up against last year's Australian finalist Cibulkova of Slovakia.
The world number one snuffed out a spirited challenge from 24th seeded Spaniard Garbine Muguruza to stay on track in her quest for a sixth Australian major, which would also guarantee she retains the top ranking.
The 33-year-old won 2-6, 6-3, 6-2, admitting "I didn't start out so well" as she dropped her second opening set in as many matches.
However, the reigning US Open champion is so supremely confident that she said she could always find another gear, even against a player who bounced her out of last year's French Open.
"I've been playing for a long time. When I have to go up a level, I have to," she said.
With the job done against Muguruza, Serena took time out to cheer from the stands during Venus' roller-coaster 6-3, 2-6, 6-1 win against sixth seed Agnieszka Radwanska.
The elder Williams sister is shaping as the feelgood story of the tournament as she continues to roll back the years, reaching the quarter-finals of a Grand Slam for the first time in five years.
"Obviously she didn't really look like a 34-year-old," a stunned Radwanska said. "She was quick. She was fresh, playing very well."
The win takes her 2015 record to 9-0, including winning the Auckland Classic lead-up event, but took its toll on Venus, who said she "went into a trance" during the third set.
It continues a remarkable comeback from injury and a long battle with the energy-sapping Sjogren's Syndrome, which was diagnosed in 2011.
"Now is my moment and I want to keep this moment going," she said.
Another player seen as out of the reckoning for honours before the tournament started was 11th seed Cibulkova, who has struggled at Grand Slams since losing last year's decider to China's Li Na.
She was expected to fall to two-time champion Azarenka of Belarus, who was unseeded this year after an injury-plagued 2014 but expected to go deep into the tournament she once dominated.
Instead it was the diminutive Cibulkova who drew inspiration from Rod laver Arena, winning 6-2, 3-6, 6-3 as she zipped around the court chasing lost causes and firing them back at Azarenka with interest.
"I just walked on the court and all the great memories came to my mind and I was just thinking 'I'm a great player, I can do it, I just have to believe in myself'," she said.
Keys racked up the only straight sets victory of the day in her all-American clash with Madison Brengle.
Long touted as the rising star of American tennis, Keys said she was finally ready to step up under the guidance of Davenport, a three-time Grand Slam champion who won the Australian title in 2000.
"I think I've matured a little bit and just got my game together a little bit more. It's kind of just come together," she said.
Results from day eight of the Australian Open at Melbourne Park on Monday:
Stanislas Wawrinka (SUI x4) bt Guillermo Garcia-Lopez (ESP) 7-6 (7/2), 6-4, 4-6, 7-6 (10/8)
Kei Nishikori (JPN x5) bt David Ferrer (ESP x9) 6-3, 6-3, 6-3
Milos Raonic (CAN x8) bt Feliciano Lopez (ESP x12) 6-4, 4-6, 6-3, 6-7 (7/9), 6-3
Novak Djokovic (SRB x1) bt Gilles Muller (LUX) 6-4, 7-5, 7-5
Dominika Cibulkova (SVK x11) bt Victoria Azarenka (BLR) 6-2, 3-6, 6-3
Serena Williams (USA x1) bt Garbine Muguruza (ESP x24) 2-6, 6-3, 6-2
Madison Keys (USA) bt Madison Brengle (USA) 6-2, 6-4
Venus Williams (USA x18) bt Agnieszka Radwanska (POL x6) 6-3, 2-6, 6-1