Wimbledon champion Serena Williams has now won 25 of her past 26 matches.

Story highlights

Serena Williams wins her first match just four days after victory in the Wimbledon final

American returned to the U.S. to defend her title at Stanford hard-court event

Teen opponent idolized Williams as a child, and was even her ballgirl at age 12

Williams will face South African sixth seed Scheepers in quarterfinals

CNN  — 

Just four days after winning her fifth Wimbledon crown, Serena Williams overcame the effects of jet lag to successfully begin the defense of her Bank of the West Classic title in Stanford, California.

The American made a smooth transition from the London grass courts – which she will return to for the Olympics later this month – and an eight-hour time difference as she beat college champion Nicole Gibbs 6-2 6-1 in the second round of the hard-court event.

“I definitely felt a little sluggish today, but it was fine, and it was good to get that win,” Williams told reporters after winning against the 19-year-old wildcard entrant to register her 25th victory in 26 matches.

“It’s really bright out there too – I was so used to all the gloom in London and all the clouds

“I’ll feel better after having tomorrow off and more time to get adjusted. I’m still waking up at like two in the morning.”

Gibbs, who is also the NCAA doubles champion, idolized Williams as a child, even serving as a ballgirl for her at age 12.

“When I played Monica Seles for the first time it was pretty cool. To think someone would still want to be like me is kind of awesome,” the 30-year-old Williams said.

Gibbs won her opening match against Thailand’s world No. 174 Noppawan Lertcheewakarn, who did not make it through qualifying at Wimbledon, but found a much tougher challenge in 14-time grand slam champion Williams.

“It was a great experience – it was really good to match up against that level and see what’s out there,” said Gibbs, who was appearing in the main draw of a WTA Tour event for the first time.

“She’s such a hero in my mind and so built up in my mind, but I think I was definitely more in the match than I had anticipated being. After a few points I felt I could at least compete at that level.”

Williams was full of praise for her opponent too, adding, “I think she played really well – she moves really well and she doesn’t quit, and I think that’s the best quality you can have as an athlete, and especially as a tennis player.

“She could have easily given up and she didn’t. She’s a fighter. And she has a really good first serve. I think she really held her own today.”

Williams will next face sixth seed Chanelle Scheepers after the South African beat Portuguese wildcard Michelle Larcher de Brito to reach her first top-level quarterfinal.

“Serena will definitely be a challenge, but I’m ready to go out and just enjoy it,” said Scheepers, who lost to Williams in straight sets in their only previous meeting.

“I’m happy with how the hard-court season has started and I hope to keep this up.”