Stephanie Dubois was the first Canadian to fall at the US$2.168 million women's Rogers Cup tennis tournament as the Laval, Que., veteran dropped a 1-6, 6-3, 6-0 decision to Chanelle Scheepers on Tuesday night.
Dubois breezed through the first set at Uniprix Stadium, breaking service three times, but then could no longer hold her own serve, losing it seven straight times against the 41st-ranked South African.
Scheepers advanced to a second-round meeting with 14th-seeded Flavia Pennetta.
The 25-year-old Dubois, ranked 151st, beat Scheepers in their own previous meeting in a lower level tournament in 2008.
She was among three Canadians who got wild card entries into the draw along with Aleksandra Wozniak, who plays Daniela Hantuchova later Tuesday, and Wimbledon junior champion Eugenie Bouchard, who opens play Wednesday against Shahar Peer.
The 16 seeded players have a bye to the second round, including top-seeded Victoria Azarenka.
Azarenka arrived directly from the London Olympics, where she won bronze in singles and then took gold in mixed doubles with Belarus compatriot Max Mirnyi.
Only a few weeks earlier on the same court, she had reached the semifinals of Wimbledon, where she lost to Serena Williams.
"It's not easy to regroup mentally because you want to celebrate a bit, but you have no time," Azarenka said. "You have to go back to the tennis court and practise.
"But I'm happy to be here. I can't wait to start this tournament and just play tennis again."
Azarenka, the top seed, will open against Austrian Tamira Paszek, who won her first match 6-2, 6-1 over Julia Goerges of Germany.
Two qualifiers opened with victories as Sesil Karatantcheva of Kazakhstan, who turns 22 on Wednesday, blanked Sorana Cirstea of Romania 6-0, 6-0 and Jana Cepelova of Slovakia beat Sweden's Sofia Arvidsson 6-3, 6-3. Cepelova's next test is against eighth-seeded Italian Sara Errani.
Roberta Vinci of Italy overcame deficits of 4-1 and 5-2 in the third set deficit to defeat Yarina Wickmayer of Belgium 6-2, 3-6, 7-5, while Carla Suarez Navarro topped Maria Jose Martinez Sanchez 1-6, 6-4, 6-3 in an all-Spanish matchup.
Simona Halep downed Michelle Larcher de Brito 6-4, 6-3 and next will play 4th-seeded Samantha Stosur.
Azarenka is hanging onto the No. 1 world ranking by a thread and will have to hold off second seeded Agnieszka Radwanska and No. 3 Maria Sharapova to stay on top. Sharapova can regain the top ranking if she wins the tournament, while Radwanska would need to win and have both Azarenka and Sharapova bow out before the quarter-finals.
"It's really exciting," said Azarenka, who got her first grand slam title this year at the Australian Open. "We're all showing consistent tennis through the year.
"We're all winning tournaments. It's exciting for people to watch when it's close and we're doing our best competing against each other. It's definitely going to be interesting by the end of the year."
The hardcourt tournament began a day later than usual and will end on Monday night to accommodate the London Olympics.
At Uniprix Stadium
Purse: $2.17 million (Premier)
Roberta Vinci, Italy, def. Yanina Wickmayer, Belgium, 6-2, 3-6, 7-5.
Ekaterina Makarova, Russia, def. Urszula Radwanska, Poland, 6-4, 6-2.
Jana Cepelova, Slovakia, def. Sofia Arvidsson, Sweden, 6-3, 6-3.
Tamira Paszek, Austria, def. Julia Goerges, Germany, 6-2, 6-1.
Sesil Karatantcheva, Kazakhstan, def. Sorana Cirstea, Romania, 6-0, 6-0.
Carla Suarez Navarro, Spain, def. Maria Jose Martinez Sanchez, Spain, 1-6, 6-4, 6-3.
Simona Halep, Romania, def. Michelle Larcher de Brito, Portugal, 6-4, 6-3.
Chanelle Scheepers, South Africa, def. Stephanie Dubois, Canada, 1-6, 6-3, 6-0.
Aleksandra Wozniak, Canada, def. Daniela Hantuchova, Slovakia, 7-5, 7-6 (5).
Ksenia Pervak, Kazakhstan, def. Anna Tatishvili, Georgia, 7-6 (6), 7-6 (4).
Vera Dushevina, Russia, and Tamarine Tanasugarn, Thailand, def. Janette Husarova, Slovakia, and Shahar Peer, Israel, 7-5, 5-7, 10-7 tiebreak.
Natalie Grandin, South Africa, and Vladimira Uhlirova, Czech Republic, def. Darija Jurak, Croatia, and Katalin Marosi, Hungary, 6-7 (4), 6-4, 10-8 tiebreak.
Ekaterina Makarova, Russia, and Olga Savchuk, Ukraine, def. Liga Dekmeijere, Latvia, and Alicja Rosolska, Poland, 3-6, 6-1, 10-8 tiebreak.
Anastasia Rodionova, Australia, and Galina Voskoboeva, Kazakhstan, def. Alla Kudryavtseva, Russia, and Mandy Minella, Luxembourg, 6-0, 6-3.
Anastasia Pavlyuchenkova, Russia, and Lucie Safarova, Czech Republic, def. Timea Babos, Hungary, and Eleni Daniilidou, Greece, 6-1, 3-6, 11-9 tiebreak.
Klaudia Jans-Ignacik, Poland, and Kristina Mladenovic, France, def. Nuria Llagostera Vives and Maria Jose Martinez Sanchez, Spain, 7-6 (8), 6-3.