Swiss Roger Federer and Spaniard Rafael Nadal have joined Wimbledon champion Andy Murray to pull out of next week's Toronto Masters tennis tournament.Seventeen-time Major champion Federer on Tuesday said he would like to take more time after Wimbledon while Nadal, who has 14 Grand Slam titles, still is recovering from his wrist injury, reports Xinhua.That leaves Serbian world No.1 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 the Toronto event which runs from July 25 to July 31.The "big four" are expected to take part in the Rio Olympic Games which start on August 5.