World number one Aryna Sabalenka said she still had room for improvement after a second dominant win in the Brisbane International on Thursday.
Sabalenka was pushed at times by 36-year-old Sorana Cirstea but was never really troubled by the Romanian as she notched a 6-3, 6-3 win to reach the quarter-finals of the season-opening tournament.
The Belarusian will next play Madison Keys, the American who beat her in last year's Australian Open final.
Keys came back from a set and a break down to overcome Russia's Diana Shnaider in a three-hour marathon 6-7 (5/7), 7-6 (7/5), 7-6 (7/4).
There was a shock in the last of the night's matches when Ukraine's Marta Kostyuk stunned world number three Amanda Anisimova 6-4, 6-3 in a high-quality match on centre court.
Sabalenka said she aimed to get better as she targets a third Australian Open title in four years when the first Grand Slam of the year begins in Melbourne on January 18.
"I think there is always room to improve, and I'm definitely not at my peak," Sabalenka said.
"Of course I prefer to win every match 6-0, 6-0, like everyone probably prefers, but at the end of the day you only get better when someone pushes you and you have to deal with moments under pressure."
Sabalenka said tournaments such as Brisbane, which features seven of the top 10 women, were perfect preparation for a Grand Slam.
"I think it's important to have quality matches before heading to the big event, just so you're preparing yourself mentally for fights, for battles," she said.
"And playing against top players is definitely a huge help heading into the Grand Slam tournament."
- 'Drama' -
Keys, who won her first Grand Slam title in Melbourne over Sabalenka, was in trouble against 21-year-old Shnaider but was able to stay in the contest and edge ahead in the last two tiebreaks.
"That had a little bit of everything. It's good to start the year with a little bit of drama, so I'm glad we got that out of the way," Keys said.
Kostyuk played the match of her life to down Anisimova, who reached the finals of Wimbledon and the US Open in 2025.
"I practised with Amanda a week ago and she absolutely destroyed me," Kostyuk said.
"I think I played really, really good. I had an amazing preparation and tactically I think I played really good."
Former Wimbledon champion Elena Rybakina reached the quarter-finals with a 6-3, 6-2 win over Spain's Paula Badosa.
World number five Rybakina took control at 3-3 in the first set, winning nine of the next 11 games to seal victory.
Fourth seed Jessica Pegula also came back from a set down beat Ukraine's Dayana Yastremska 5-7, 6-2, 6-3.