SERENA WILLIAMS: Her Shortest Match of the Tournament

World number one Serena Williams marched into the Australian Open fourth round on Friday, showing no mercy in a 6-1, 6-1 demolition of hapless teenager Daria Kasatkina.

The six-time Melbourne Park winner and defending champion easily out-muscled the overawed Russian on Rod Laver Arena in just 44 minutes, the shortest match of the tournament so far.

It sets her up with a fourth-round clash against another Russian, Margarita Gasparyan, with a quarter-final beckoning against old foe Maria Sharapova -- a showdown Williams would be confident of winning.

She has beaten Sharapova in every match they have played since 2004.

"I think I played well today. It was one of those days where everything I did went right," said the 34-year-old, who offered some word of encouragement to Kasatkina.

"She has such a bright future. She's so young and she's headed in the right direction."

Playing on centre court against the top seed at a Grand Slam was a huge occasion for the 18-year-old, who was not only making her debut at the tournament but is on her first ever trip to Australia.

The teen only played her first WTA tournament last April, but has so far managed to score three wins over top 50 opposition, signalling her promise.

She came into the event as the world's 69th-ranked player but was no match for the composed and massively experienced American, who is gunning to equal Steffi Graf's Open-era record of 22 Grand Slam titles.

The powerful Williams wasted little time in laying down the law, winning a break for a 2-0 lead with Kasatkina barely getting her racquet on the ball as she was pushed around the court.

Kasatkina managed to get on the scoreboard in holding serve for 1-3 but she had no answers to Williams' serve as the American rattled through the set in just 22 minutes.

After her second-round win, Williams said she was pleased by her consistency and lack of errors, and it was a similar story on Friday.

The American, who dropped only three matches in 56 last season, made few mistakes in a dominant display and broke in the first game of the second set with outgunned Kasatkina struggling against the Williams weaponry.

She didn't give up and won a service game to be 1-2, but that was as good as it got as Williams cantered to the finish line.

Williams won three majors -- the Australian and French Opens and Wimbledon -- last year which took her to within one of Graf's long-time record of 22.

She claimed her first Australian Open title in 2003, beating sister Venus in the final, and reached her sixth last year when she toppled Sharapova.