* Murray calls out trainer midway through second set
* Defending champion Djokovic advances to third round
(Updates with quotes and Djokovic match)
TORONTO, Aug 8 (Reuters) - 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.
"I feel on the grass courts the muscles get tired but the
joints not so much, but on the hard courts the knees, ankles and
hips take quite a fair pounding," Murray, whose match was his
first on a hard court since early March, told reporters.
"And because I haven't had enough days to adjust to the
surface that's probably why there were a few aches and pains."
The Briton, who appeared to hurt himself while chasing down
a forehand, occasionally rubbed his left knee and had about five
minutes of massage on his left quadriceps while leading the
final set 3-2.
Still, the second seed, who is scheduled to face big-serving
Canadian Milos Raonic in the third round, managed to chase down
drop shots and held his serve throughout the 82-minute match.
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 6-4 7-6 to
compatriot Jeremy Chardy.
Del Potro, whose Olympic semi-final loss to Roger Federer
five days ago was the longest men's three-set match played in
the professional era, admitted fatigue got the better of him
during a 6-4 7-6 defeat to Czech Radek Stepanek.
"It's not easy to play after a big effort in the Olympics,"
the sixth seeded Argentine told reporters. "Now I need time to
recover my body if I want to stay healthy."
Del Potro, who was playing his first match since beating
Djokovic for the bronze medal at the Olympics on Sunday, also
said he had no doubt he would be ready for the Aug. 27-Sept. 9
U.S. Open, where he won his sole grand slam in 2009.
In other action, fourth seed Tomas Berdych rallied for a 6-7
6-4 6-4 win over Julien Benneteau in a match that lasted just
over three hours, while ninth seed Gilles Simon fell 6-2 6-2 to
Germany's Tommy Haas.
Fifth seed Janko Tipsarevic of Serbia was a 7-6 6-4 winner
over Russia's Mikhail Youzhny, Croatian 10th seed Marin Cilic
breezed by Greece's Marcos Baghdatis 7-5 6-3 and German 15th
seed Florian Mayer fell 6-3 6-4 to Spain's Marcel Granollers.
(Reporting by Frank Pingue; Editing by Mark Lamport-Stokes and
Daniel Magnowski)