Kvitova fights back from knife attack to shine

New York - Battling back after a home-invasion knife attack last December that jeopardised her career, two-time Wimbledon winner Petra Kvitova matched her top US Open performance Sunday by reaching the quarter-finals.

The 13th-seeded Czech left-hander ousted Spanish third seed and reigning Wimbledon champion Garbine Muguruza 7-6 (7/3), 6-3 to book a Tuesday last-eight date with US ninth seed and seven-time Grand Slam winner Venus Williams.

Kvitova, who also reached the 2015 quarter-finals, is playing only her eighth event of the year after left hand surgery following a break-in assault last December that is still under investigation by Czech police.

"Especially after everything that happened, I do feel little bit pumped," Kvitova said. "I don't really have the best ranking, but on the other hand I know I can play well, which I showed today.

"I worked hard to come back and be here. It means a lot."

Kvitova, whose All England crowns came in 2011 and 2014, said after her victory in Arthur Ashe Stadium that her journey back from the attack has been a difficult climb.

"It was a tough time. All five months were very tough. It was just a journey I didn't know how it would end.

"If it ends here on the big stage it's a happy end."

Kvitova has a greater appreciation for the tour lifestyle after an injury that put her career at risk.

"I'm very grateful that I can be part of it again," Kvitova said. "The life is still a little bit strange, but it's getting better. It's much more easier for me to feel more normal than before."

She said her hand is not yet fully healed but has come far enough for her to produce formidable performances.

"I think still my hand is not 100 percent ready, so I do feel I have space to improve," Kvitova said. "I'm still working on the strength. I'm really not thinking about it when I'm playing much. I'm just taking how it is.

"Movement is still not great, but for the grip of the tennis racquet it so far is OK."

Kvitova has earned the her rivals' respect, none more so than Williams, who is only 1-4 lifetime against the Czech.

"What she has gone through is unimaginable, unreasonable," Williams said. "The world we live in is just shocking. So for her, I think to be playing well is such a blessing.

"To be able to come out here and do what she needs to do, to clear her head, it's such a beautiful thing to see. What else can I say except I'm glad to see her back?"

Muguruza found Kvitova's form astonishing considering what she has been through.

"I think it's incredible that she's playing at this level," Muguruza said. "I think she's playing very well. So I don't feel she has changed.

"She's one of the biggest hitters and a talented player. She has a great timing and a lot of power."

Muguruza could become world number one for the first time, unless current number one Karolina Pliskova makes the final or fourth seed Elina Svitolina reaches the semi-finals.

"I think every player dreams to be number one at some point," Muguruza said. "I didn't come to the US Open to be number one... that wasn't really my goal.

"We'll see. I'll keep on eye now on the scores. But that's it."