TORONTO -- Serena Williams earned a 6-0, 6-3 first-round victory against Ukraine's Alona Bondarenko at the Rogers Cup on Tuesday.
The winner of 13 Grand Slam tournaments aced her second serve of the match.
No. 2 seed Kim 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.
The American got through the first set in 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 Williams' imposing serve and forehand.
Williams, who is working her way back from a foot injury that put her out of the WTA's top 100, is using the tournament as warmup for the U.S. Open.
Although she rolled on Tuesday, Williams stopped short of saying she's Grand Slam-ready.
"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 left the match with a reported stomach muscle problem.
It was her seventh appearance at the tournament, having won it in 2005 against Justine Henin.
Despite winning the Australian Open, Clijsters has been hampered this year by injuries. She injured her right ankle in April and then withdrew from tournaments in Rome and Madrid.
Canadians Stephanie Dubois and Aleksandra Wozniak advanced with first-round victories.
Dubois earned a 7-6 (4), 6-1 win over German qualifier Kathrin Woerle while Wozniak, from Blainville, Quebec, sailed past Israel's Shahar Peer 6-1, 6-0.
Serbia's Ana Ivanovic breezed past Chinese qualifier Shuai Zhang 6-1, 6-1. The 2006 champion hasn't advanced past the second round of the tournament since 2007.
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.
Murray out in Montreal
MONTREAL -- Two-time defending champion Andy Murray is heading home early from the Rogers Cup.
Murray was upset, 6-3, 6-1, by Kevin Anderson in the second round in Montreal.
Murray, who had a bye in the first round, was seeded fourth. He's also fourth in the ATP rankings, while his South African opponent is ranked 35th.
Murray, who won the 2009 Rogers Cup in Montreal and defended his title last year in Toronto, said his South African opponent's serve is the best part of his game.
"If he serves well -- it's a very fast court, it's tough to break -- he can be dangerous," Murray said.
Also, Canada's Vasek Pospisil reached the second round with a 4-6, 6-3, 6-4 win over 22nd-ranked Juan Ignacio Chela of Argentina.