Seventeen-time major champion Federer’s last match was his loss to Canadian Milos Raonic in the Wimbledon semi-finals, while Nadal, who has won 14 titles in Grand Slam tournaments, has not played since withdrawing from the French Open in May with a wrist injury.
World number three Federer has won the Toronto event twice in his career, but also missed the tournament last year.
“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,” the Swiss great told Tennis Canada.
“Looking ahead, it is best for me that I take more time after Wimbledon.”
Spain’s Nadal has still not recovered from the problem that forced him to end his campaign at Roland Garros when it was just two matches old.
“I am disappointed to announce I won’t be able to come to Toronto to play this year,” said Nadal. “I only started practising a week ago after my wrist injury and I am not ready to play such an important event.”
Reigning Toronto champion Murray announced his decision to skip the tournament on Monday, saying that he too needed more time to recover from winning his third major title.
That leaves Serbian world number one Novak Djokovic, who suffered a shock third-round defeat to American Sam Querrey at Wimbledon, as the only member of tennis’ “big four” taking part in Toronto.