Two-time defending champion Petra Kvitova needed just an hour to beat Ekaterina Makarova 6-3 6-1 and move into the semi-finals of the Connecticut Open, despite suffering from a cold.
Looking to join Venus Williams and Caroline Wozniacki as a four-time winner in the tournament, Kvitova overpowered the Olympic doubles champion, breaking her four times - three during the 25-minute final set.
"I think that sometimes I can't really pay too much attention how I feel," Kvitova said. "It's just going out there, just being strong mentally, think about the next point, think about the tennis."
The Olympic bronze medallist and two-time Wimbledon champion has been criticised during her career for inconsistent play.
But the Czech star will be looking for her fifth consecutive appearance in the finals here and her third straight title. She also won in 2012.
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"It's always nice to coming somewhere when you feel, you know, at a home and you know you can play well. It always gives you little bit more confidence than normally."
She will face top-seed Agnieszka Radwanska of Poland in the semi-finals. Radwanska beat lucky loser Kirstin Flipkens of Belgium 6-1 6-4.
The world's fourth-ranked player had an easy time in the first set, but needed a break in the ninth game of the second set to secure the win over the 30-year-old Flipkens, who struggled with an injury to her left hand.
Ukraine's Elina Svitolina advanced with a 6-3 6-1 victory over Elena Vesnina, Makarova's double's partner in Rio.
Svitolina outran her Russian opponent and took advantage of 33 unforced errors.
"I was trying to push her to make those errors," she said. "I think in the end she was just going for too much."
The 21-year-old Svitolina will play Johanna Larsson, the 28-year-old Swede who upset second-seeded Roberta Vinci of Italy 7-6 (9-7) 6-1.
