Serena Williams returned to action for the first time since pulling out of Wimbledon with a straight-sets win over Karolina Pliskova in Stanford, USA.
The world number one had to retire from a doubles match with her sister, Venus, at Wimbledon on 1 July with what proved to be a virus.
Williams, 32, saw off Karolina Pliskova of the Czech Republic 7-5 6-2 at the Bank Of The West Classic on Wednesday.
"I'm still taking it a match at a time," said the American.
|Williams won the title on her last two appearances in Stanford in 2011 and 2012, and has now won 10 consecutive matches at the Californian event|
"I'm just worried about doing what I want to do and what I've been practising on the court. But I wasn't feeling any nerves today. I felt good. And I felt fine physically."
Williams had taken some time off after Wimbledon, recuperating with a holiday in Croatia before returning to practice.
The 17-time Grand Slam champion will play fifth seed Ana Ivanovic or Canadian qualifier Carol Zhao in the Stanford quarter-finals.
Second seed Agnieszka Radwanska suffered a surprise 6-3 3-6 6-4 defeat by world number 59 Varvara Lepchenko of the USA.
In Washington, Britain's Jocelyn Rae and Anna Smith beat top seeds Cara Black and Sania Mirza 6-4 6-3 to reach the semi-finals of the Citi Open.