Britain's Heather Watson was forced to retire with a shoulder injury in the first round of the Rogers Cup in Toronto, Canada.
Watson, 25, was trailing Japan's Naomi Osaka 6-1 4-1 when the world number 71 signalled she was unable to continue.
Meanwhile, British number two Kyle Edmund also lost his first round match to world number 33 David Ferrer in Montreal.
The 22-year-old went down 6-7 6-4 6-3 to his Spanish opponent.
Britain's world number one Andy Murray has withdrawn from the Rogers Cup as he has yet to recover from the hip injury which hampered his Wimbledon campaign.