Defending women's champion Sofia Kenin has been knocked out of the Australian Open, losing in straight sets to Kaia Kanepi in the second round.

Estonian Kanepi, 35, dominated throughout, hitting 22 winners to Kenin's 10 and saving all seven break points she faced at Melbourne Park.

Unseeded Kanepi will face Croatian 28th seed Donna Vekic in the third round.

Kenin, who acknowledged that she was struggling with the pressure of being defending champion after her first-round win, was nowhere near her best against Kanepi, making 22 unforced errors.

The big-hitting Kanepi beat Simona Halep at the 2018 US Open when the Romanian was world number one and has made an excellent start to 2021, reaching the final of last week's Gippsland Trophy in Melbourne.

"I served really well today, I think this helped a lot. My gameplan was to play aggressive as I usually do," said Kanepi.

Meanwhile, world number one Ashleigh Barty overcame fellow Australian Daria Gavrilova 6-1 7-6 (9-7) to move into the next round.

Barty looked set for a routine win when she served for the match at 6-1 5-2, but Gavrilova broke twice to force a second-set tie-break.

The 24-year-old, who did not play for almost a year because of the coronavirus pandemic, saved set points before securing the victory.

Afterwards, Barty said the second set "was turning into a bit of a prickly pear" but she was "happy to bring it back around in the tie-break when I needed to and win some big points". Next up for Barty is Russian 29th seed Ekaterina Alexandrova.

She was joined in the third round by sixth seed Karolina Pliskova, who saw off American Danielle Collins 7-5 6-2 and will now play fellow Czech Karolina Muchova.

Swiss 11th seed Belinda Bencic outlasted Russian veteran Svetlana Kuznetsova 7-5 2-6 6-4 to set up a meeting with Belgian 18th seed Elise Mertens, who beat China's Lin Zhu 7-6 (10-8) 6-1.