STANFORD, Calif. -- Serena Williams and big sister Venus know their newfound focus on doubles is sure to affect their energy in singles. They're willing to make that sacrifice if it leads to more Grand Slam titles together.
Neither top-seeded Serena nor second-seeded Venus showed off their best tennis Tuesday night, each still doing plenty right for straight-set victories in their first-round singles matches at the Bank of the West Classic.
Serena broke serve three times in the opening set but needed a second-set tiebreaker to beat gutsy Li Na of China 6-3, 7-6 (6) a couple of hours after Venus' 6-2, 6-3 win over Stephanie Dubois of Canada in this $700,000 tournament at Stanford.
Li trailed 6-2 in tiebreaker but came back to tie it at 6-6 before Serena finally capitalized on her seventh match point.
"I was too anxious and ready to go home and was playing a tough player who never gives up," Serena said. "Obviously I can play better. I think I hit five first serves in the whole match. I'm a little off. That's fine. I'd rather be a little off now than later."
The Williams sisters were back on court for their first competition since Serena beat Venus at Wimbledon.
After some post-Wimbledon down time, it wasn't always pretty. Serena overcame seven double faults and showed her frustration at times after leading 4-1 in the second set. She bounced her racket off the ground and caught it in the first.
While Venus looked far from sharp during spurts as she missed shots long and sent others into the net, she pulled out enough of her top shots when it mattered. Same for Serena.
Could it be another all-Williams final come Sunday?
Venus has reached the finals in six of her seven previous appearances at the Bank of the West Classic.
Serena is making only her second appearance at Stanford. She reached the semifinals in 2008, but injuries kept her from competing in other years when she had planned to participate.
Ranked second in the world, Serena already has two Grand Slam wins this year at the Australian Open and Wimbledon.
They are excited about their doubles prospects, too. They'll be back on the court together Wednesday for their second-round match.
"We kind of have this secret goal I can't talk about," Venus said.
Serena wouldn't elaborate much.
"Our dream is no longer," she said. "I can't get a better partner, I just don't think so. She gets everything."
After Venus Williams and Dubois failed to hold serve through the first three games of the opening set, Williams cruised the rest of the way in the first meeting between the two.
"It was a great match to get my rhythm, hit a lot of balls and work on my shots," said Williams, who won titles here in 2000 and '02. "It's all about the mentality. I usually adjust pretty quickly. ... I do want to try new and different things."
Still a little spacey -- she admitted to some "brain freeze" -- after a few weeks of sleeping in and relaxation following her Wimbledon runner-up showing to Serena, Williams said: "We love playing in L.A. I'm sorry, not L.A., I mean California. It feels like home for us."
Wozniak, who recently took four weeks off, became the first Canadian in 20 years to capture a Tour title when she won the tournament last year.
In other first-round matches, eighth-seeded Marion Bartoli of France defeated Japan's Ayumi Morita 7-6 (6), 6-3; Maria Kirilenko topped Anna Chakvetadze, the 2007 champion in this event, 6-4, 5-7, 7-6 (5); fourth-seeded Jelena Jankovic beat qualifier Angela Haynes 6-3, 6-1; Samantha Stosur upset sixth-seeded Dominika Cibulkova 6-4, 6-3; Sabine Lisicki beat American qualifier Lilia Osterloh 6-2, 6-3, and qualifier Alla Kudryavtseva of Russia downed France's Julie Coin 6-1, 7-6 (5).
In the doubles, Anne Keothavong of Britain -- teaming with Morita -- was forced to retire from the match due to a left knee injury. She was to be taken to a hospital for further tests.