Vintage Venus on a roll in booking last-eight berth at Australian Open

Seven-time grand slam champion Venus Williams rolled back the years to reach the Australian Open quarter-finals for the first time in five years on Monday, setting up an intriguing matchup with Madison Keys, the teenager touted as the future of American tennis.

In the last match of the day, Novak Djokovic reached his 23rd consecutive grand slam quarter-final with a 6-4, 7-5, 7-5 win over Luxembourg's Gilles Muller. Djokovic is trying to become the second man after Roy Emerson to win five Australian Open titles. He is also aiming for his eighth major title overall.

Williams, meanwhile, battled fatigue in a tough three-setter, the 34-year-old finished strongly to win 6-3, 2-6, 6-1 and stun Polish sixth seed Agnieszka Radwanska, sealing match point with an ace to celebrate her return to the big time.

Cheered on from the stands by top-seeded sister Serena, an exhausted Venus somehow found the energy to get past highly rated Radwanska.

"In the third, I think I went into a trance. I just wanted to win," the ecstatic 18th seed said.

The win takes her 2015 record to 9-0, including winning the Auckland Classic lead-up event.

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 all year and then next year too, but it will take work," she said. The lanky American looked like the Venus of old early in the match, covering the court with ease to blast venomous returns and pinpoint accurate winners.

Radwanska, 25, tried to tire her opponent out by extending the rallies and moving her around, but admitted she was surprised at Venus' resilience.

"Obviously, she didn't really look like a 34-year-old," said the Pole, a semi-finalist at Melbourne Park last year. "She also had tough matches before. But she was quick. She was fresh, playing very well."

Her win throws up the enticing prospect of the first all-Williams meeting at a grand slam since the 2009 Wimbledon final. The draw means the siblings would meet in the semis if they make it through the quarters.

But first she has to get past Keys, a teenager who was only two when Venus made her first grand slam appearance in 1997.

"Apparently she started playing because she saw Serena and I. She started watching me when she was in diapers," she said.

"I was 19 once, I beat players who were more experienced. So at the end of the day, if you can hit the ball in the court enough times and get enough points on your side, that will be who wins, no matter what the numbers are."

Venus flagged as the match wore on, clocking up 36 unforced errors, but hung on grimly.

She moved briskly in the first set, notching a hard-earned break in the seventh game that stretched more than 12 minutes and eventually taking it.

Agence France-Presse, Reuters