Before anyone rushes to talk up the chances of Venus Williams winning her first Australian Open title, it is worth remembering that she will face stiffer challenges than the one posed to her by Ying-Ying Duan. Williams could hardly have wished for a more deferential opponent than Duan, who resembled little more than a hitting partner for the American.

The only positive for Duan after a painfully lopsided contest was the minor triumph of winning a game at the end of a first set that quickly assumed the feel of an exhibition. The world No87 from China left with her pride just about intact but still in need of major surgery after a crushing 6-1, 6-0 defeat and a brisk workout for Williams, who was detained for 58 minutes having admitted she knew “zero” about her opponent before the match.

It means the 13th seed should be fresh for her next assignment, which sees her meet Mona Barthel in the fourth round after the unseeded German edged out Australia’s Ashleigh Barty, the world No223.

Still going strong at the age of 36, Williams is yet to drop a set in Melbourne and she dismantled Duan with some gorgeous tennis, torturing the 27-year-old with 25 winners. But there are plenty of sharks left in the water. While Williams will be the heavy favourite against Barthel, the world No181 who recovered from a break down in the third set to defeat Barty 6-4, 3-6, 6-3, she will be conscious that the remaining heavyweights on her side of the draw enjoyed commanding wins.

After failing to convince in her first two matches, Angelique Kerber raised her level against Kristyna Pliskova, beating the Czech 6-0, 6-4. The match had been billed as an opportunity for Pliskova to avenge her twin sister Karolina’s defeat to the world No1 in last year’s US Open final. Fat chance. Kerber was relentless from the start and the defending champion played herself into form before meeting the USA’s Coco Vandeweghe, who halted Eugenie Bouchard’s revival by beating the Canadian, a semi-finalist in Melbourne three years ago, 6-4, 3-6, 7-5.

Garbiñe Muguruza, the No7 seed, emulated Kerber and Williams by reaching the last 16 in two straightforward sets. The French Open champion dropped six games en route to victory over Latvia’s Anastasija Sevastova, the 32nd seed, and she can be forgiven if she is already making mental preparations for a quarter-final against Kerber.

The Spaniard has to deal with Sorana Cirstea first, though, after the unseeded Romanian reached the fourth round of a major for the first time thanks to a 6-2, 7-6 win over the USA’s Alison Riske.

If Williams beats Barthel, she will face a Russian in the last eight. Svetlana Kuznetsova took the long route against Jelena Jankovic, outlasting the experienced Serbian to win 6-4, 5-7, 9-7.

The No8 seed will need a swift recovery before her match against Anastasia Pavlyuchenkova, who beat Elina Svitolina 7-5, 4-6, 6-3.