A bad day for women's big guns at Sydney International

Russian teen Daria Kasatkina has confirmed she will be one to watch at the Australian Open, tuning up with an impressive straight-sets win over world No.1 Angelique Kerber at the Sydney International.

Kasatkina was far too composed in her second meeting with Kerber, who won grand slams in Melbourne and New York last year to claim top spot on the women's rankings.

The 19-year-old triumphed 7-6 (7-5), 6-2 in 92 minutes, storming into the third round of the Sydney tournament by breaking the top seed's serve on five occasions.

Kerber committed 41 unforced errors, including a loose stroke that resulted in Kasatkina taking the first-set tiebreak.

The Russian next faces Johanna Konta, who beat Australian Daria Gavrilova 6-1, 6-3 in just 81 minutes.

Twenty-five--year-old Konta did not look back after breaking in the opening game and is now the only seed left in the top half of the draw.

Kerber was among a handful of top seeds to fall on Tuesday.

Defending champion Svetlana Kuznetsova has fallen in the second round of the Sydney International, going down to Russian compatriot Anastasia Pavlyuchenkova.

World No.9 Kuznetsova was one of three top seeds to fall early on Tursday's third day at Homebush, including world No.6 Dominika Cibulkova and No.18 Roberta Vinci.

After ousting Australian Samantha Stosur on Monday, world No.27 Pavlyuchenkova won her first career meeting with Kuznetsova 7-5 6-3.

Pavlyuchenkova will next meet former Wimbledon finalist Eugenie Bouchard, who took advantage of an error-riddled Cibulkova 6-4 6-3 to claim her fourth win in five clashes.

It was also the Canadian star's third win over a top-15 opponent in her past 12 matches, giving her some much-needed confidence ahead of next week's Australian Open.

"Any time you play one of the best players in the world - I think she's ranked five right now - it's like a standard of where you're at," Bouchard said after the match.

"It was okay. I mean, I feel like I could play better tennis. I feel at times we both kind of were making unforced errors, but we were also pressuring each other to make mistakes.

"I have taken a couple of solid steps this week, but I'm far from where I want to be. Even though I won, to me, I could do a lot of things better."

Also on Tuesday, ninth-seeded Italian Vinci had no answers for fellow veteran Barbora Strycova of the Czech Republic, losing 6-2 6-3.