Sabalenka, who arrived in Montreal with a chance to claim the number one spot from Iga Swiatek, showed plenty of fight in the nearly three-hour centre court battle but won only two of 13 break points while making 11 double faults, many at key moments.

Samsonova got two breaks from six chances which helped the 15th-seeded Russian into the last eight where she meets Swiss Belinda Bencic, a 6-7(3), 6-3, 6-1 winner over seventh-seeded Czech Petra Kvitova in a clash of former champions.

Both players will have little time to savour the upsets with their quarterfinal set for later on Friday.

“Honestly it is going to be difficult, it’s going to be hard. I’ll try to save all the energy I can,” said Samsonova, who has just two wins over top-five ranked opponents – both against Belarusian Sabalenka.

Sabalenka, winner of three titles this season including the Australian Open, blasted 13 aces but more than offset those with double faults and one gave Samsonova the decisive break to move 5-3 ahead in the third, allowing her to serve out the match.

“Last year I played unbelievable in the States in general and this year I’m going crazy,” said Samsonova, who opened the North American hardcourt season last week with run to the semifinals in Washington.