Britain's world number one Andy Murray has withdrawn from the Rogers Cup as he has yet to recover from the hip injury which hampered his Wimbledon campaign.
The 30-year-old Scot said he was "disappointed" to miss next week's tournament in Montreal and Toronto, but added: "I am doing everything I can to return as quickly as possible."
Murray could lose his number one ranking to Rafael Nadal next week, and he remains a doubt for the US Open, which begins on 28 August.
Earlier on Thursday, five-time Grand Slam champion Maria Sharapova withdrew from the event, and Tennis Canada confirmed world number six Marin Cilic has also pulled out.