Andy Murray battled some pain but showed no signs of an Olympic hangover as the gold medallist moved into the last 16 of the Toronto Masters, while a fatigued Juan Martin del Potro was one of five seeds ousted on Wednesday.
Murray, playing his first match since his triumph at the London Games on Sunday, called out a trainer late in a 6-1, 6-3 win over Italian Flavio Cipolla, which he later attributed to a change of playing surfaces from grass to a hard court.
Defending champion Novak Djokovic cruised to a 6-2, 6-3 win over Australian Bernard Tomic in 71 minutes, setting up a third-round match with American Sam Querrey, who upset 13th seed Kei Nishikori of Japan 6-2, 6-3.
Third seed Frenchman Jo-Wilfried Tsonga was the highest seeded player eliminated on Wednesday, falling 4-6, 6-7 to compatriot Jeremy Chardy. Del Potro lost 4-6, 6-7 defeat to Czech Radek Stepanek.
Fourth seed Tomas Berdych rallied for a 6-7, 6-4, 6-4 win over Julien Benneteau, while ninth seed Gilles Simon fell 6-2, 6-2 to Germany's Tommy Haas.