Brisbane - Top seed and defending champion Elina Svitolina crashed out of the Brisbane International at the hands of Belarusian Aliaksandra Sasnovich on Wednesday.

In a replay of last year's final, Sasnovich reversed that result as she ousted Svitolina 6-4, 0-6, 6-3.

The Belarusian displayed some breathtaking shot making in the first set before Svitolina stormed back in the second.

But Sasnovich continued to go for her shots and broke Svitolina twice in the third set to seal victory and book a quarter-final against Croatian Donna Vekic.

Vekic continued her good form when she downed Dutchwoman Kiki Bertens in three sets 7-6 (7/5), 1-6, 7-5.

Vekic looked in trouble when she was down 4-5 in the third with Bertens serving for the match, but the Croatian fought back to win the next three games and book her place in the quarter-finals.

"I'm really happy to have this kind of match in the first tournament, to see how much I can push myself," she said.

"Obviously I can play long, play good and win, so I'm really happy about that."

Estonia's Annet Kontaveit caused a boilover when she beat fourth seeded Czech Petra Kvitova 7-5, 7-6 (7/1).

Kontaveit, whose compatriot Kaia Kanepi won this tournament in 2012, was too consistent for Kvitova, who was backing up after a three-hour first-round win over Danielle Collins late Tuesday afternoon.

"We played each other quite a lot of times last year so I knew it was going to be tough from the beginning," Kontaveit said.

"I was just trying to hang in there in the second set. I'm just so happy."

Latvian Anastasija Sevastova earlier thrashed British qualifier Harriet Dart 6-2, 6-0.

Former champion Karolina Pliskova downed fellow countrywoman Marie Bouzkova 7-5, 6-2 and will face off against Australia's Alja Tomljanovic in the quarter-finals.

Tomljanovic secured her place in the last eight with a 6-2, 7-6 (7/2) win over Britain's Johanna Konta.