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 number one 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.