Bartoli was forced to battle through illness before claiming victory
France's Marian Bartoli overcame a bout of illness to beat British qualifier Melanie South in the first round of the Rogers Cup in Montreal.
Bartoli needed on-court treatment during the second set for a stomach bug, which has affected a number of players at the tournament.
The 10th seed eventually came through 6-3 6-7 (5-7) 6-0.
"I was not feeling good at all and the doctor gave me tablets but I had to hang in tough," said Bartoli.
"I was not feeling good at all. My legs were shaking. My arms were shaking by themselves. I was really dizzy. I got cold.
"The tablets helped a lot in the third set but it took a while for me to feel a little better. But I needed to come up with the win."
Bartoli was told by a member of the medical staff at the tournament that between 15 and 20 players have contracted the virus.
"They told us to wash even more our hands and not touch the same food as the others, or drink the same water - to be really careful because there's a virus going on," she added.
There were also wins for ninth seed Patty Schnyder, who advanced when Yuan Meng of China retired with a thigh injury, and Petra Kvitova of the Czech Republic who beat Aiko Nakamura of Japan 6-2 6-4 to line up a match with top seed Ana Ivanovic.
Qualifier Michelle Larcher de Brito, the 15-year-old from Portugal who reached the round of 16 two weeks ago in Stanford, continued to impress with a 2-6 6-3 6-3 victory over American Vania King.
The top eight seeds have a bye into the second round.
The event could be a battle for the world number one ranking between Ivanovic, Serbian compatriot Jelena Jankovic and Maria Sharapova.
The three are only 202 points apart, with 430 points up for grabs for the Rogers Cup winner.