Australian Open champion Caroline Wozniacki surprisingly joined Maria Sharapova in exiting the WTA Rogers Cup, but world number one Simona Halep advanced to the quarter-finals.
Rising Belarusian Aryna Sabalenka knocked out world number two Wozniacki in three sets before losing her last-16 clash later on Thursday.
Former world number one and five-time grand slam winner Sharapova was no match for sixth seed Caroline Garcia in Montreal.
French Open champion Halep played twice on Thursday and won both matches to reach the last eight at the expense of an ailing Venus Williams.
WOZNIACKI CRASHES OUT
Wozniacki had three match points but suffered a 5-7 6-2 7-6 (7-4) loss to Sabalenka.
This match was initially scheduled for Wednesday but rain forced it to be postponed until Thursday.
And the Dane – playing for the first time since Wimbledon – proved wasteful as Sabalenka rallied from a 5-3 deficit in the final set to prevail after two hours, 31 minutes.
"I didn't win any of the match points," Wozniacki said. "I had an opportunity. I didn't get it… I feel like I would have felt after the finals: it's obviously disappointing losing a match like this when you have the opportunity."
Sabalenka then lost 2-6 7-6 (7-1) 6-0 to 14th seed Elise Mertens, who will meet defending champion Elina Svitolina in the last eight.
GARCIA EASES PAST SHARAPOVA
It was a routine outing for Frenchwoman Garcia, who swept aside Sharapova 6-3 6-2.
Garcia was a class above against the Russian star as she moved through to her seventh quarter-final of the season.
Top seed Halep stands in the way of Garcia a spot in the Rogers Cup semi-finals.
After surviving the challenge of Anastasia Pavlyuchenkova in a rain-affected match, Halep defeated Williams – who was struggling with a knee injury – 6-2 6-2.
"I saw that Venus was not feeling great, so we cannot talk about this match too much," Halep said. "But I'm happy even in this situation I could win the match."
SVITOLINA KEEPS TITLE DEFENCE ALIVE
Defending champion and fifth seed Svitolina secured a quarter-final berth after accounting for Johanna Konta 6-3 6-4.
Svitolina won the last four games of the match from a break down to advance in less than 90 minutes.
Konta was back on the court having completed a 6-3 6-1 win over two-time major winner Victoria Azarenka.
Meanwhile, US Open champion Sloane Stephens moved into the next round, but Petra Kvitova was beaten.