Serena battles into Montreal semi-finals
Serena Williams of the USA serves to Caroline Wozniacki of Denmark in their quarterfinal match during the Rogers Cup at Uniprix Stadium on August 8, 2014 in Montreal, Canada - by Streeter Lecka
Williams, who lifted the 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.