Maria Sharapova's US Open preparations took a major blow with the Russian World No 2 forced to withdraw from next week's WTA event in Toronto.
The 28-year-old Russian withdrew due to a right leg strain, tournament organisers said on Friday.
Sharapova has not played since she lost to World No 1 Serena Williams in the Wimbledon semi-finals on July 9 and has played just 10 tournaments so far this year.
The Rogers Cup in Toronto is a key stop on the North American hardcourt circuit before the year's final grand slam at Flushing Meadows in New York from Aug. 31-Sept 13.
Pliskova continues her ascent with semi berth at Stanford
Karolina Pliskova advanced to the semi-finals of the Bank of the West Classic with a 6-2, 6-4 win over Croatia's Ajla Tomljanovic on Friday.
Win or lose Pliskova will push herself into the top-10 for the first time when the new rankings are released on Monday.
Only world number one Serena Williams (40-1) has won more matches than Pliskova (38-14) this season.
The World No 11 will meet American Varvara Lepchenko in the semi-finals on Saturday while Ukraine's Elina Svitolina will play Germany's Angelique Kerber at the tournament in Stanford.
Lepchenko defeated Mona Barthel of Germany 6-7, 6-2, 6-3 while Svitolina advanced with a 4-6, 7-5, 6-1 win over American Alison Riske.
Germany's Kerber came from behind to beat Poland's second seed Agnieszka Radwanska 4-6, 6-4, 6-4.
