Maria Sharapova has been knocked out of the US Open.
"I will try my best".
It was the most significant match since Kvitova's comeback from the horrendous hand injuries she suffered when she was stabbed by an intruder at her home last December.
Kvitova's power from the baseline proved too much after she held serve before breaking again in the 11th game but the topsy-turvy set continued as Muguruza broke back immediately to force a tie-break, where the former composed herself to hit the front.
However, she has now taken out the Wimbledon champion and handed Elina Svitolina and Karolina Pliskova a shot of ending the event as world No. 1.
"I'm not thinking like that anymore", she said.
After such a dominant summer, the manner of the loss will concern Muguruza - who had dropped just nine games on her way to the last-16 - whose forehand broke down with Kvitova taking full advantage.More news: Pessimism as Kushner sets off for Israeli-Palestinian talks
"I think that she's playing awesome on the majors this year".
Kvitova made it through to the quarterfinals with a 7-6 (3), 6-3 win over No. 3 seed Garbine Muguruza on Ashe Stadium Sunday night. But sometimes I just really feel that the touch is there, the strength, the aggressive kind of game plan of it is there, which I'm really, really appreciative for that. I feel very happy.
Muguruza still has a chance to claim the No. 1 ranking after this tournament.
The Czech star reached the quarter-finals in NY for the second time in three years after a 7-6 (7-3) 6-3 win over third seed Muguruza on Sunday. After winning that game, Muguruza gained a little confidence and definitely gave Kvitova a hard time closing the match out.
Petra Kvitova of the Czech Republic in action against Garbine Muguruza of Spain during their fourth round match.
She is in the Grand Slam quarterfinals for the first time since the 2015 United States Open. "That's why probably I am playing more relaxed and more free maybe", she told a news conference.
"What she's gone through is unimaginable, unreasonable", Williams said.