AUCKLAND, Australia (AFP) — Coco Gauff stepped up preparations for the Australian Open with an emphatic 6-3, 6-0 win over rising Czech Brenda Fruhvirtova at the Auckland Classic on Thursday to march into the quarterfinals.

After a few issues at the start in which US Open champion Gauff dropped her first service game and had to save two break points on her third, the 19-year-old proved unstoppable in the battle of the teens.

The 16-year-old qualifier Fruhvirtova, who beat world No. 48 Anna Blinkova in the first round, won only 10 points in the second set of a match that was over in 70 minutes.

"She started off playing very well and I was able to raise my level. I thought I served well and I did better on the returns," said Gauff, who sent down five aces.

The American will next play eighth seed Varvara Gracheva, the world No. 42.

On the other side of the draw, seventh seed Petra Martic of Croatia beat China's Yue Yuan 6-2, 6-2 and will play the winner of the match between second seed Elina Svitolina and Emma Raducanu.

Former US Open champion Raducanu has slipped to 301 in the world after being sidelined by injury for the past eight months.

The Australian Open starts on 14 January.