Serena Williams breezed into the second round of the Rogers Cup with a straight sets win over Alona Bondarenko on Tuesday, while second seeded Kim Clijsters retired from her match with abdominal muscle injury.
Williams, a winner of 13 Grand Slam tournaments, beat Ukraine's Bondarenko 6-0, 6-3 to set up a second-round meeting with Germany's Julia Goerges.
Clijsters withdrew from her second-round match in the second set while leading 6-3, 1-2 against China's Zheng Jie.
"I still have a few weeks till (the U.S. Open) and we'll try to do everything to be ready," said Clijsters, who won the tournament in 2005.
Williams got through the first set in just 16 minutes using her speed and power, as a bewildered Bondarenko scattered across the court helplessly.
Bondarenko put up some fight early in the second, but could do little to contain the American's imposing serve and forehand.
Although she was in command throughout, Williams said there is still room for improvement heading into the U.S. Open.
"I would hate to be Grand Slam-ready right now, seeing as how the U.S. Open is not right now, so I'll try to peak at the right time," Williams said. "I want to get better on a few things. I definitely want to try and continue to do more and play harder."
Clijsters shook her head after hitting a forehand and immediately retired. Despite winning the Australian Open, Clijsters has been hampered all year by injuries. She injured her right ankle in April and then withdrew from tournaments in Rome and Madrid due to right shoulder and wrist injuries.
Ana Ivanovic, Andrea Petkovic and Agnieszka Radwanska were among the high-profile first-round winners on Tuesday while Dominika Cibulkova and Jelena Dokic also retired with injuries.
Serbia's Ivanovic breezed past Chinese qualifier Zhang Shuai 6-1, 6-1. The 2006 champion will face Iveta Benesova in round two. Benesova progressed when Cibulkova retired when up a break in the third set. The score was 7-5, 4-6, 1-3.
Germany's Petkovic, seeded 11th, won 6-2, 6-2 over 17-year-old Canadian Eugenie Bouchard after a rain delay of almost 3-1/2 hours. Petkovic will next face Hungary's Greta Arn.
No. 13 seed Radwanska was a 6-4, 6-1 winner over Russia's Elena Vesnina. The Pole's next opponent will be Croatian qualifier Petra Martic, who staged a big turnaround to beat Czech Lucie Hradecka 1-6, 6-4, 6-4.
Canadians Stephanie Dubois and Aleksandra Wozniak excited home fans with first-round victories. Dubois earned a 7-6 (4), 6-1 win over German qualifier Kathrin Woerle while Wozniak sailed past Israel's Shahar Peer 6-1, 6-0.
In other action Tuesday: Roberta Vinci got past Yanina Wickmayer 6-4, 6-2; China's Shuai Peng eliminated Spain's Lourdes Dominguez Lino 6-1, 7-5; Spaniard Anabel Medina Garrigues topped Italy's Sara Errani 7-5, 6-1.
Serbia's Bojana Jovanovski won against Jelena Dokic after the Australian retired in the first set; Italy's Flavia Pennetta was a 6-3, 6-1 winner over Russia's Maria Kirilenko; and Slovakia's Daniela Hantuchova won 6-3, 6-4 over Argentina's Gisela Dulko.