Ailing Petra Kvitova, the two-time Wimbledon champion and the bookmakers' favourite for the 2017 title, said she felt like a "slow animal" in her shock second round exit on Wednesday.

The Czech 11th seed lost 6-3, 1-6, 6-2 to

America's Madison Brengle who has made the third round for the first time.

Kvitova, who was playing in her second Grand Slam since recovering from a terrifying knife attack in her home, needed to call for medical assistance during the third set.

As well as having her blood pressure taken, the 27-year-old required an on-court examination by a doctor after complaining of breathing difficulties.

"1 just couldn't breathe, and I was feeling a bit sick, as well," said Kvitova.

"That sometimes happens. But, yeah, unfortunately it happened at Wimbledon, which is not nice.

"But she still played what she could. She hit everything back. It was just tough for me to still have the energy to put it back and play my aggressive game."

Kvitova feared she would never play tennis again after suffering serious injuries to her left playing hand fighting off a burglar at her Czech home in December.

She returned at Roland Garros, making the second round, before winning the Birmingham grass court title.

That success prompted many to tip her for a third Wimbledon crown to add to her 2011 and 2014 victories, especially with Serena Williams and Maria Sharapova both absent.