The 2011 champion beat the 19th seed 7-6 (5) 6-3 on Monday to set up a last-eight clash with Belgium’s Kirsten Flipkens.
But Kvitova believes she was not at her best out on Court 3 and attributes her subdued performance to a heavy bout of nerves.
“I didn’t play my best today, especially in the first set,” Kvitova said in her post-match news conference.
“I was pretty nervous today because I knew I had quite a good chance to beat her and to be in the quarter-final .
“I think I need to be more relaxed, for sure, in the beginning of the match. If I’m looking back on today’s match, that’s something that I really need to do.”
As a previous champion, the eighth seed is the highest-ranked player left in her half of the draw – though she feels this only adds to the weight of expectations on her shoulders.
“I think there’s a little bit more pressure because everybody expects me to win,” Kvitova continued. “That’s something that isn’t easy.
“I’m not thinking about it [the 2011 title] right now. I mean, that’s two years ago. This is a different year, a different tournament for me.
“Everybody is saying that I’m the highest seeded player in my half and that I’m already supposed to be in the final. That’s something that’s not really easy to hear.”
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