Roger Federer and Rafael Nadal have pulled out of next week's Rogers Cup, Tennis Canada confirmed on Tuesday.
World number three Federer said he needed more rest after his run to the Wimbledon semi-finals earlier this month, while Nadal has not featured since withdrawing from the French Open in May with a wrist injury.
Tuesday's announcement follows confirmation that Wimbledon winner and reigning Rogers Cup champion Andy Murray will also not feature at the ATP 1000 event in Toronto, also citing the need for rest.
"I have made the tough decision to withdraw from the Rogers Cup," said Federer. "Toronto is one of my favourite events on the calendar and I am disappointed that I won't be able to compete in front of the great tennis fans in Canada.
"Looking ahead, it is best for me that I take more time after Wimbledon. I look forward to coming back to Canada next year and I wish [tournament director] Karl Hale and everyone at Tennis Canada a very successful tournament."
"I am disappointed to announce I won't be able to come to Toronto to play this year," added Nadal.
"I only started practicing a week ago after my wrist injury and I am not ready to play such an important event.
"I am very much looking forward to playing in Toronto in a couple of years since I have always been treated great in that tournament and have a lot of great Canadian fans."
Canada's Vasek Pospisil will now take his place in the main draw, with the other spot to be taken by a wildcard entry.