Garbine Muguruza stepped up her Australian Open preparations by sending down 13 aces Thursday while battling into the semi-finals of the Shenzhen Open.

Spain’s former world number one defeated Zarina Diyas of Kazakhstan 6-4, 2-6, 6-4 to reach her first semi-final since winning a title in Monterrey, Mexico last April.

The 26-year-old Muguruza, now ranked 35 in the world and the sixth seed, faces fifth seed Ekaterina Alexandrova of Russia in the last four in southern China.

“I did a good pre-season, I worked very hard,” said Muguruza, the two-time Grand Slam champion who endured a poor second half to 2019.

“There’s not a secret to success. When you work hard, in the end things will pay off.

“Stay there when things don’t go well and keep fighting through. Good things will come.”

The other semi-final will be between unseeded Kristyna Pliskova of the Czech Republic and Kazakhstan’s seventh seed Elena Rybakina.

Rybakina booked her place with a 6-4, 4-6, 6-2 victory over the third seed Elise Mertens of Belgium.

Mertens follows top seed Belinda Bencic and second seed Aryna Sabalenka – who was the defending champion – out of the Shenzhen Open.

The Australian Open, the first Grand Slam of the year, begins in under a fortnight.