Serena Williams refused to blame a rolled ankle for her incredible Australian Open loss to Karolina Pliskova, instead giving credit to her opponent.

Williams gave up a 5-1 lead in the final set and squandered four match points in a 6-4 4-6 7-5 quarterfinal loss at Rod Laver Arena on Wednesday.

The 23-time grand slam champion appeared to roll her ankle when serving in the seventh game and Pliskova took charge from that point.

But Williams, 37, said her ankle was not the reason she suffered defeat.

"My ankle seems to be fine. I usually don't know until the next day," the American told a news conference.

"I think she just played lights out on match point, literally, hitting lines. Just went for, just went crazy on match point. She just played unbelievable on match point."

Williams lost 25 of the final 33 points of the match, including being broken to love twice.

She said: "I think she just played well on my serve after that point. I think she just kind of started playing really, really good. I don't think it had anything to do with my ankle, per se. I just think she was just nailing and hitting shots."

"Obviously I made some mistakes, but she played really well after that."