Elina Svitolina handed world number one Angelique Kerber her first defeat of the year, dumping the top seed out of the Brisbane International quarter-finals.

Svitolina displayed her full potential in 2016 by beating both Kerber and Serena Williams when they respectively topped the WTA rankings, and another tenacious performance here could set her up for a profitable 2017.

Kerber was swiftly behind the eight ball, dropping serve in the opening game as her attempts to dominate from the baseline often resulted in off-target shots.

The German found her radar in the second set, but Svitolina was undimmed, scampering around court and fully deserving a 6-4 3-6 6-3 success.

Third seed Karolina Pliskova represents a tricky semi-final opponent for Svitolina after beating Roberta Vinci 3-6 6-2 6-2.

Alize Cornet sprung another shock, defeating second seed and WTA Finals champion Dominika Cibulkova 6-3 7-5.

France's Cornet was the only non-seeded player remaining in the competition and her record of one semi-final appearance last year is already matched for 2017 after Cibulkova could not capitalise on a fast start, in which she burned four break points in Cornet's first two service games.

Cornet beamed: "What a start of the year! It's the first week and I think my game is not so bad!

"Beating a player like Dominika takes an amazing performance. Everybody knows how much she fights and hits hard the ball. I'm just very, very, very happy."

Garbine Muguruza fought off fatigue to book a meeting with Cornet, overcoming Svetlana Kuznetsova 7-5 6-4.

The fourth seed, Muguruza had played a pair of three-set matches to reach the quarter-finals, but was able to dispatch of the Russian more comfortably.

"My previous matches were very, very tough, and I felt a little bit tired," the Spaniard said. "But I was very, very motivated so I kind of forgot that I was tired."