BRISBANE - The Brisbane International lost its top two women's seeds Thursday when Angelique Kerber and Dominika Cibulkova were both bundled out in the quarter-finals of the season-opening tournament.

World number one Kerber made 48 unforced errors, including five double faults, as she went down to Ukraine's Elina Svitolina 6-4, 3-6, 6-3, while Frenchwoman Alize Cornet eliminated Cibulkova 6-3, 7-5. Kerber started slowly against Svitolina, who broke the German early and held the advantage to take the opening set.

Kerber struck back in the second and appeared to take command of the match when she broke Svitolina at the start of the third. However, the sixth seeded Ukranian broke back to level the set, then broke again to move to 5-3, holding comfortably to claim her fourth win against Kerber in nine meetings.

Kerber said she wasn't worried about how the early loss would affect the defence of her Australian Open crown. "I think Grand Slams are always completely different," she said. "It doesn't matter how you play before. Of course, it's always good to have matches, especially at the beginning of the year. I have had two good matches here. I will try to have a few more matches before Melbourne (at the Sydney International next week)."

Svitolina will now take on third seeded Czech Karolina Pliskova, who came back from losing the first set to Italian Roberta Vinci to win her quarter-final 3-6, 6-2, 6-2. In the first match on Pat Rafter Arena, Cornet was in irresistable form as she blunted everything Cibulkova threw at her to win a tight struggle in 123 minutes.

A more settled and mature Cornet said there was no reason why she couldn't get back into the world top 20 for the first time since 2014. "I've always had a lack of consistency during my career and maybe the fact that I'm 26, I'm a little bit older now, I have more experience and I feel like maybe I'm touching something during this week of Brisbane," she said.  "I handle my emotions much better and I think that's how I got some really great victories here. I don't want to say that it's done, but definitely when I see myself playing like this, I believe that I can go higher in the rankings."

She now faces reigning French Open champion Garbine Muguruza, who edged Russia's Svetlana Kuznetsova 7-5, 6-4. Fourth seed Muguruza started slowly against Kuznetsova before closing out the match in one hour, 50 minutes. The Spaniard has now been on court for almost seven and a half hours in her opening three rounds but although she admitted to being tired, she said it was good preparation for the Australian Open. "I'm not worried -- I know with Cornet it is going to be a battle, she's a fighter, so I expect another touch match," Muguruza said.