Laura Robson took just three games as she was blown away by Petra Kvitova in the third round of the Southern California Open in Carlsbad.
Robson has risen to 32 in the rankings after some impressive displays this year, including reaching the last 16 at Wimbledon.
But she was unable to produce the goods against third-seed Kvitova as she slumped to a 6-1 6-2 loss.
It was a measure of revenge for the world number seven, who suffered a surprise second-round loss to the British teenager in this year's Australian Open.
The 19-year-old struggled for rhythm in the opening set and could only manage a first-serve percentage of 41 while also registering five double faults.
That inconsistency was quickly exploited by her Czech opponent, who broke Robson twice to wrap up a one-sided set.
The Briton at least put up more of a fight at the start of the second, exchanging breaks of serve with Kvitova early on.
But the third seed then stepped up a level and ended any resistance from Robson with two further breaks to put the match to bed in one hour and 15 minutes.
"I didn't know exactly what to expect from myself because the first match after preparing for the US hardcourts is always difficult, plus I lost to her at the Australian Open," said Kvitova.
"But this is tennis, and every day is different, and that's how I approached the match. I played well and my serve was great today. We practiced very hard on my serve back home after Wimbledon."
Top seed Victoria Azarenka celebrated her 24th birthday with a 6-2 6-3 second-round win over former French Open champion Francesca Schiavone.
The Belarussian is playing this week for the first time since limping out of Wimbledon with a knee injury.
"I missed playing and I was just happy to be able to do something I've been training for," said Azarenka.
"I enjoyed the time I had to go through rehab and learn so many new things. I was excited to see how I would handle it in the match.
"It was a good feeling to have that platform, and I'll just try to make it better and better now."
Also on Wednesday, fourth-seeded Roberta Vinci of Italy advanced with a 6-4 6-2 victory over American Bethanie Mattek-Sands.
Vinci will next face either US qualifier Coco Vandeweghe or former world number one Ana Ivanovic.
Ivanovic, the seventh seed from Serbia, rallied to beat defending champion Dominika Cibulkova 4-6 6-3 6-2 in the last match of the first round.
Fifth seed Sam Stosur won the night match against Sesil Karatantcheva in straight sets, 6-4 6-1 in an hour and 12 minutes.