World No. 1 Roger Federer has withdrawn from the Rogers Cup in Toronto, Tennis Canada announced. Federer, who edged Juan Martin del Potro in a four-hour, 26-minute semifinal today to reach the Olympic final, joined a slew of other withdrawals for next week’s event, including Spaniards Rafael Nadal, David Ferrer, Nicolas Almagro and Fernando Verdasco,  France’s Gael Monfils, Swiss Stan Wawrinka and American Andy Roddick. Novak Djokovic and Andy Murray, who squared off in today's second Olympic semifinal, are the top two seeds in Toronto.