Li Na battled through a tight first set then coasted to a 7-6 (7/1), 6-2 victory over Dominika Cibulkova on Friday to reach the semi-finals of the WTA Toronto tournament.
The fourth seed from China, playing her first tournament since a quarter-final appearance at Wimbledon, needed an hour and 36 minutes to get past unseeded Slovakian Cibulkova, who launched her hardcourt build-up to the US Open with the Stanford title a fortnight ago.
Li is trying to improve on a runner-up finish in Canada last year. Her semi-final opponent could be the woman who beat her in the final at Montreal in 2012 -- Petra Kvitova.
The sixth-seeded Czech was playing unseeded Romanian Sorana Cirstea in the quarter-finals.
Third-seeded Agnieszka Radwanska also reached the semi-finals, with a 7-6 (7/1), 7-5 victory over fifth-seeded Sara Errani.
In a match that featured a total of 15 service breaks, Poland's Radwanska managed to hold in the final game of the contest to secure the victory and avenge a quarter-final loss to the Italian at Roland Garros this year.
After an early exchange of breaks in the third set, Radwanska broke Errani for a 5-4 lead, but dropped her serve in the next game.
She broke Errani again for a 6-5 lead and a chance to serve for the match, and this time made no mistake, taking a 40-15 lead and securing the win after two hours and one minute with a thumping forehand that Errani couldn't get back.
In the semi-finals world number four Radwanska will face either world number one Serena Williams or Slovakian Magdalena Rybarikova.
While Rybarikova is unseeded in this $2.369 million tournament she arrived in Toronto riding the momentum of a second straight title in Washington.