Leading by a set and a break, Keys looked to be easing into the semifinals. However, a spirited Kvitova comeback ensured the match went down to the wire, Keys eventually closing out a 6-3, 6-7(2), 7-6(5) victory after two hours and 41 minutes.
"I think I played a pretty solid first set today, then she raised her level. I just think at the end it became a couple of points here or there. I think I got my serve back on track a little bit," Keys said. "I mean, really, it could have gone either way. It was really close."