US Open finalist Jessica Pegula eased past Maria Sakkari to reach the quarter-finals of the Adelaide International on her return from injury.

The top seed defeated her Greek opponent 6-4 6-1 in just 73 minutes in Wednesday's last-16 tie, as she warms up for the Australian Open.

The American, who received a bye for the first round in Adelaide, will next play her compatriot Ashlyn Krueger, who defeated Spain's Paula Badosa 7-6 (7-4) 6-7 (4-7) 6-2.

"It's always tough getting the first win of the year, you don't know what to expect," Pegula said.

"But it's good heading into Melbourne next week. My focus is on doing well here first. It's fun to problem-solve on court and have a good attitude to start the year."

Pegula had not played since withdrawing from the WTA Finals in November with a knee injury.

Meanwhile, defending champion Jelena Ostapenko was knocked out of the tournament by 2022 winner Madison Keys, who beat the eighth seed 3-6 6-4 6-3.

Second seed Emma Navarro defeated Ekaterina Alexandrova 7-6 (7-4) 6-4 in a battle that lasted two hours and will now face Liudmila Samsonova, who overcame Belinda Bencic 7-6 (7-3) 4-6 6-4.

Keys will now take on Russian Daria Kasatkina after she beat Australia's Emerson Jones 7-5 6-3.

Two-time Wimbledon runner-up Ons Jabeur also exited the tournament after a 6-2 6-4 defeat to Kazakhstan's Yulia Putintseva, who will next battle Diana Shnaider, who received a walkover after Marketa Vondrousova retired, for a place in the semi-finals.

Meanwhile, at the Hobart International, top seed Dayana Yastremska of Ukraine defeated Ann Li 1-6 7-5 6-2 to set up a quarter-final clash against McCartney Kessler, who overcame Argentina's Maria Lourdes Carle 6-2 6-2.

In the other last-eight ties, third seed Amanda Anisimova will meet sixth-seeded Elina Avanesyan, Sofia Kenin faces Maya Joint and second-seeded Elise Mertens takes on unseeded Veronika Kudermetova.