Sixth-seeded Caroline Wozniacki recorded her first-ever victory over a reigning World No. 1 player on Friday with a 7-5, 6-7 (3), 6-4 win over Karolina Pliskova to advance to the semifinals of the Rogers Cup in Toronto.
Inclement weather wreaked havoc on the match, as the start was delayed for more than two hours because of rain while three more interruptions ensued once play began.
Wozniacki, who is a former World No. 1, broke the Czech at love to get back on serve at 4-4 of the deciding set. The Dane then held serve and followed with another break to dismiss Pliskova in 2 hours, 56 minutes and advance to the semifinals of the Toronto event for the first time.
"I thought she started off really strongly and she was attacking and playing really, really well," Wozniacki said. "After that, I feel like I stepped a little bit closer to the line just to try and take away a little bit of time. I once I kind of got on a roll, I started serving better.
"I just tried to stay steady, tried to take the ball on the rise and try to stay aggressive when I could and keep my serves aggressive too."
"(Pliskova) had a great year and she's been playing really well. I don't really think about (beating a No. 1) too much," Wozniacki said. "I knew I was going to play someone that was really tough today, and I'm just happy with my win and that's really it."
Pliskova lamented several miscues she made in the first set.
"I think the biggest mistake was in the first set -- so because of that, I think I lost," the 25-year-old Pliskova said. "Overall, I think the match was much longer than just the hours on the court. It's just tough to play her in these conditions. She's putting everything back, so obviously, I did some mistakes."
American Sloane Stephens also needed three sets before posting a 6-2, 1-6, 7-5 victory over Czech Lucie Safarova.
Stephens won the last four games and saved three match points to upend Safarova in 2 hours, 11 minutes. She benefited from Safarova's eight double faults as well.
In other quarterfinal matches, defending champion and second-seeded Simona Halep of Romania faced off with Frenchwoman Caroline Garcia while fifth-seeded Elina Svitolina of Ukraine challenged fourth-seeded Spaniard Garbine Muguruza.