Melbourne, Australia (SportsNetwork.com) - World No. 1 Serena Williams and former top-ranked star Venus Williams secured berths in the quarterfinals at the 2015 Australian Open.
Serena dropped the first set before rallying to top rising 24th-seeded Spaniard Garbine Muguruza 2-6, 6-3, 6-2 in two hours at Melbourne Park on Australia Day.
Muguruza stunned Serena at the French Open last year, handing the American, who won just four games in that match in Paris, the worst loss of her Grand Slam career in the process.
The 33-year-old American great blitzed her 21-year-old opponent with 17 aces and won 38 of 49 first-serve points on Monday.
"It was a great match -- congratulations to Garbine, she played so well," Serena said.
The 18-time Grand Slam champion and reigning U.S. Open titlist owns five Aussie Open titles, but none since 2010.
Her quarterfinal opponent will be 11th-seeded Slovak Dominika Cibulkova, who doused on-the-mend Belarusian star Victoria Azarenka, 6-2, 3-6, 6-3.
Azarenka led 2-0 in the third set, but couldn't hold on against the diminutive Cibulkova.
"Today I wasn't thinking about the score, I was just going for it," Cibulkova said. "And when I was up, I was going for it even more.
"I always have tough matches with Vika. The tennis she plays goes well with mine," Cibulkova added.
Cibulkova was last year's Aussie runner-up to since-retired Chinese star Li Na.
The former world No. 1 Azarenka is a two-time Aussie Open champ and two-time U.S. Open runner-up. Her 2014 season was interrupted by a foot injury and she's been trying to re-locate her game since last spring.
This marks Azarenka's earliest exit from the Aussie since 2011.
"I take it as progress. I think there are a lot of the positive things to take from here," she said. "Overall, I can be pretty happy."
In other fourth round action on Day 8 of the fortnight, an 18th-seeded Venus reached her first major quarterfinal since 2010 and remained undefeated in 2015 by surprising sixth-seeded former Wimbledon runner-up Agnieszka Radwanska 6-3, 2-6, 6-1 and rising Madison Keys vanquished fellow American Madison Brengle 6-2, 6-4. Brengle reached her first-ever WTA final in Hobart two weeks ago.
Venus will clash with the 19-year-old Keys in an all-American quarterfinal on Wednesday.
Venus is a seven-time Grand Slam champion who was the 2003 Aussie runner-up to her younger sister. She's a perfect 9-0 this year, including a title in Auckland three weeks back.
The 34-year-old Venus was asked what her inspiration has been to keep plugging away all these years.
"Definitely my sister Serena," she replied. "She's just the ultimate champion. She definitely gives me a lot of inspiration. And of course all of my fans, who've always stayed behind me."
Keys will play in her first-ever Grand Slam quarterfinal when she faces Venus.
"It feels really good," she said. "My mom texted me before the tournament. She said, 'It's your last Grand Slam as a teenager,' and sent me a bunch of grandma faces. I'm like, 'Thanks for reminding me mom! Thank you. Love you.' But it's huge. It's my last Slam as a teenager. I hope I can keep it up."
The quarterfinals will get underway Tuesday, as second-seeded former No. 1 Maria Sharapova will battle seventh-seeded Wimbledon runner-up Eugenie Bouchard and third-seeded French Open finalist Simona Halep will take on consistent 10th-seeded Russian left-hander Ekaterina Makarova.
Sharapova is 3-0 all-time against the Canadian Bouchard, including some French Open match wins in 2013 and last year, while Halep is 1-0 lifetime versus Makarova.
The reigning French Open champion Sharapova was the Aussie champ in 2008 and runner-up in 2007 and 2012.