San Francisco Frontiers - Defending champion Keys surges into Australian Open last 16

The ninth seed won 6-3, 6-3 and will play her fellow American and sixth seed Jessica Pegula for a place in the quarter-finals.

"My serve got me out of a few tricky spots," said Keys, who is good friends with Pegula.

"I give myself a little pat on the back for that."

Keys said the emphatic nature of her victory "gives me a confidence boost that I can find my best tennis when pushed".

Keys stunned world number one Aryna Sabalenka in the final a year ago for her first Grand Slam title at age 29.

She did not win another tournament in 2025 and while she won her two opening matches in Melbourne this year in straight sets, she was nervy and admitted being "too timid".

The 33-year-old Pliskova's ranking has plummeted to 1,057 after she missed most of last season following ankle surgery.

But she has pedigree -- topping the rankings in 2017 and she is a two-time major finalist, at the US Open in 2016 and Wimbledon in 2021.

In hot and sunny conditions at Rod Laver Arena, where there was an earlier start than usual with temperatures forecast to hit 40C later in the day, Keys came out firing.

She broke the Pliskova serve twice to race into a 3-0 lead in 15 minutes and then held her own for 4-0 and wrapped up the first set in 43 minutes.

There was little between them in the second set, until Keys broke for 5-3 with a devastating forehand return that left Pliskova rooted to the spot.

"I need to trust in my game and myself," said Keys.

"I am feeling really good and I was excited for the heat today, and ready for it."

V.Perez--SFF