Melbourne - Two-time Grand Slam champion Garbine Muguruza underlined her return to form as she beat ninth seed Kiki Bertens in 68 minutes to reach the Australian Open quarter-finals on Monday.
The unseeded former world No 1 won 6-3, 6-3 on Rod Laver Arena and faces German 17th seed Angelique Kerber or 30th seed Anastasia Pavlyuchenkova of Russia in the last eight.
Just three of the top 10 seeds remain - top seed Ashleigh Barty and seventh seed Petra Kvitova meet in the quarter-finals.
The other is Simona Halep, the fourth seed, who plays Estonian 28th seed Anett Kontaveit.
The 26-year-old Muguruza reunited with Conchita Martinez, her fellow Spaniard and the 1994 Wimbledon champion, at the start of the year in the hope of reviving her failing career.
Muguruza, who has suffered a barren 18 months, said she was enjoying having Martinez on her coaching team.
"When you talk to another player you don't have to put too many words, you right away understand each other," she said.
As part of her reboot, Muguruza spent a few days in the off-season climbing Mount Kilimanjaro to clear her mind of tennis.
Muguruza ended 2019 ranked 36 in the world, the first time since 2014 that she had finished the year outside the top 20.
But she has flickered back to life in 2020, reaching the semi-finals in Shenzhen at the start of the year before pulling out of Hobart in the quarter-finals with a virus.
"First day I was not feeling good at all (in Melbourne) but every day it's improving," she said.
Muguruza emphatically won the first set in 30 minutes against a shell-shocked Bertens.
She took the momentum into the second set, breaking for a quick 1-0 lead, only to be broken back immediately.
The resurgent Spaniard broke Bertens once more for 3-2 and comfortably held for 4-2.
Muguruza broke again for a 5-3 lead and put Bertens under pressure with some powerful groundstrokes from the back of the court.
She failed to put Bertens away on the first match point but sealed the win with another big forehand, this one pinging down the line.
Results on day eight of the Australian Open Grand Slam at Melbourne Park on Monday (x denotes seeding):
Dominic Thiem (AUT x5) bt Gael Monfils (FRA x10) 6-2, 6-4, 6-4
Anett Kontaveit (EST x28) bt Iga Swiatek (POL) 6-7 (4/7), 7-5, 7-5
Simona Halep (ROU x4) bt Elise Mertens (BEL x16) 6-4, 6-4
Garbine Muguruza (ESP) bt Kiki Bertens (NED x9) 6-3, 6-3