Karolina Muchova overcomes an early deficit to eliminate top seed Ashleigh Barty at the Australian Open.

MELBOURNE, Australia -- Top-ranked Ash Barty built a big lead in her quarterfinal match at the Australian Open before her opponent took an injury timeout and left the court.

"It's heartbreaking, of course,'' Barty said.

Muchova played poorly at the start of her second major quarterfinal, and Barty raced to a 5-0 lead while losing only six points.

After nine games, Muchova had one winner and 18 unforced errors, and early in the second set, she took an injury timeout that lasted nearly 10 minutes.

"I started feeling a bit lost,'' Muchova said.

I was a bit lost on the court and my head was spinning, so I took a break.

During one stretch, Muchova won eight of nine games

Brady was in a two-week lockdown before the Australian Open because she was among the players who shared a charter flight to Australia with someone who later tested positive for COVID-19