Montreal: World number one Serena Williams clinched a gutsy 4-6, 7-5, 7-5 victory over Caroline Wozniacki on Friday to reach the semi-finals of the WTA hardcourt tournament at Montreal.
Williams, who lifted her third Canadian crown last year when the tournament was held in Toronto, battled back from a set and a break down to stretch her career head-to-head record over the 13th-ranked Dane to 7-1.
Wozniacki, a former world number one who is seeded 11th, claimed her only victory over the US star in the quarter-finals at Miami in 2012.
In Saturday`s semi-finals, Williams could find herself across the net from her sister Venus, who was due to play Spain`s Carla Suarez Navarro.
Suarez Navarro is coming off a third-round upset of French Open champion Maria Sharapova.
Wozniacki had been riding an eight-match winning streak, including a title in Istanbul in July.
Williams claimed her fourth title of the year at Stanford on Sunday, but she has disappointed in the majors this year, failing to add to her cache of 17 Grand Slam titles.
She`ll get a last chance of 2014 to do so at the US Open, which starts in Flushing Meadows on August 25.
As she has in many of her recent matches, Williams got off to a slow start against Wozniacki and the Dane was soon up 6-4, 4-2.
With the aid of an improved serve -- which yielded a total of 15 aces in the match, Williams began to assert herself.
Wozniacki twice recovered a break in the third set before Williams finally closed out the match after two hours and 41 minutes.