Garbine Muguruza admitted to being surprised by Coco Vandeweghe's "unbelievable" performance in their Australian Open quarter-final.

The hard-hitting American crushed 31 winners in a 6-4 6-0 thrashing of Spain's Muguruza on Rod Laver Arena on Tuesday.

Muguruza, the seventh seed, said she was stunned by how well the world number 35 played.

"I was surprised. I think she played unbelievable. Three times we played in the past and she didn't show this level," she said.

"I think she played very good. Her serve, her shots were there. She barely missed. So pretty good performance from her."

Despite missing a chance to reach her third major semi-final, Muguruza said there was little she could do.

"I have zero regrets about my performance," she said.

"I think when you play with someone that has the power to disturb like this, to hit these kind of shots, and has a good day, I mean, it's difficult honestly.

"But I have zero regrets for me."

Vandeweghe will face veteran Venus Williams in an all-American semi-final.