WHAT HAPPENED: No. 13 seed Petra Kvitova, in just her second Grand Slam following a career-threatening hand injury, knocked out pre-tournament favorite and No. 3 seed Garbiñe Muguruza, 7-6, 6-3, on Sunday night in Arthur Ashe Stadium.

In a battle of two of the past three Wimbledon champions, Kvitova rallied from 1-4 down in the opening set to knock out the reigning queen of the All-England Club and reach the US Open quarterfinals for the second time in her career. 

"I feel great obviously, of course. I was happy that I was managed to win the match," Kvitova said. "Over the last couple of points, I got a little bit tight. You can just dream about, but when you there, it's just different. It's about experience again. I don't really have a best ranking, but on the other hand I know I can play well, which I showed today.

"I just like to play on the big stages against the great players on the tour. I like those challenges."

Whalloping 24 winners to Muguruza's seven, Kvitova found her range after coming off second-best to Muguruza in a series of furious baselines exchanges during the early stages of the match. A crucial sixth game of the opener, where Kvitova saved three break points that would've given the No. 3 seed a 5-1 lead, helped turn the tide in her favor, as she ran off three straight games to knot the match at 4-4 at keep pace. 

Though she failed in her first attempt to serve out the set at 6-5 after securing a break, Kvitova hardly put a foot wrong in the tiebreak, as she ran off the last five points to pocket a one-set lead -- her fourth straight set won in the head-to-head.

After being broken to begin the second set, Kvitova sprinted to a two-set victory, getting back on even terms with a love break, and won four straight games to take command of the match. 

"I think it's incredible. I think it's incredible that she's playing at this level," said the Spaniard in defeat. "I'm not really familiar about what really happened. I know, of course, what happened, that she got attacked and stuff. I think she's playing very well -- so I don't feel she has changed.

"I think she was serving very good today. She finds in the key moments, big serves. She was playing good, a lot of winners. She was playing very good with the forehand today, moving well, as well."

WHAT IT MEANS: The best comeback story in tennis this season saw another chapter written on Sunday, as the Czech, who peaked at a career-high world No. 2 back in 2012, was playing her first match against a Top 10 opponent after returning to tennis in May following a home invasion where a knifed intruder slashed her left, playing hand.

Kvitova has never reached the last four in New York despite doing so at each of the other three Grand Slams on the calendar, including twice raising the trophy at Wimbledon.

She will face off for a spot in her first semifinal against Venus Williams, who advanced to the last eight after a three-set victory over Spain's Carla Suarez Navarro earlier on Sunday. 

"I watched little bit when she played today with Carla. I think that she really played great. I think that she's playing amazing on the majors this year. I mean, she is really playing very, very well on the big stages," Kvitova said. "She played the final of the Wimbledon. She's a champion. It's what we all know.

"I will try my best. I mean, she has a big serve, big server of course. She has something special which the other players doesn't have. That's what I will try to play again probably, similar game as today."

MATCH POINT: Kvitova and Williams have played three sets in each of their five career meetings. Is another dramatic battle in the cards with a spot in the US Open semifinals on the line?