Denmark's Caroline Wozniacki, last year's French Open champion Li Na and 2011 Wimbledon winner Petra Kvitova ended a marathon day of tennis by easing into the semi-finals of the $2 million tournament in convincing fashion.
They were joined by 16th seeded Czech Lucie Safarova, who will face Li in the first semi-final on Sunday, before Wozniacki and Kvitova face each other for the first time since last November's WTA Championships.
Kvitova won that clash in straight sets on the way to claiming her most recent title and will be hoping to repeat the feat to advance to Monday's final in Montreal.
Wozniacki had the most difficult passage of the last four survivors, on a day that saw several of the top seeds forced to play twice given the limited play possible on both Thursday and Friday due to rain.
The 22-year-old former number one, whose last title was in New Haven almost a year ago, first needed two-and-a-half hours to defeat American Varvara Lepchenko 4-6 6-3 6-4 in a third round match.
She returned to centre court after a four-hour break to see off a stubborn Aleksandra Wozniak 6-4 6-4 after her Canadian opponent saved five match points.
"It was tough today. Two tough matches, two long matches," Wozniacki said.
"(Kvitova) has been playing great this week. She is a great player and it is not going to be easy. I am just looking forward to getting a good night's sleep and hopefully I will be refreshed tomorrow."
Li, who has lost finals in Sydney and Rome this year, was the first to reach the semi-finals.
After toppling Sara Errani of Italy earlier on Saturday, she ended Pole Agnieszka Radwanska's hopes of reaching number one in the rankings for the first time with a confident 6-2 6-1 romp.
"I think today I played unbelievably well for both matches," Li said.
While Radwanska cruised past South African Chanelle Scheepers in a last-16 match completed earlier on Saturday, she found the Chinese number one far too good as she crashed out of a tournament she needed to win to claim top spot.
The 23-year-old world number three said she felt sapped of energy when forced to play two matches in a day.
"The first match cost me a lot of power. It was very hot conditions out there," Radwanska said. "But anyway, of course, she had the same situation. She was just playing too good. Li Na was just playing unbelievable tennis today."
Both Roberta Vinci and Tamira Paszek also struggled in their second matches of the day.
Vinci, who posted a 6-2 7-6 upset win over sixth seed Angelique Kerber in the third round, was later crushed 6-2 6-2 by Safarova in just 58 minutes.
Paszek, who thrashed Carla Suarez Navarro 6-3 6-2 in their third round encounter, proved no match for Kvitova when falling 6-3 6-2 in the other quarter-final.