British number two Heather Watson came from a set down to beat American Coco Vandeweghe 4-6 6-4 6-4 in the first round of the Mexico Open.
Watson secured the win over the former world number nine on her fourth match point after two hours, 31 minutes.
Vandeweghe is now ranked 193rd as she returns from ankle and foot injuries.
"I was just pleased with how well I fought," said Watson, 27. "I wasn't playing my best, but I stuck in there. I'm just really enjoying my tennis."
It was Watson's first match for more than two weeks since Britain's Fed Cup loss to Slovakia, which followed her defeat in round two at the Australian Open.
"I didn't feel like I had much rest," said Watson, who faces Ukraine's Kateryna Bondarenko in the next round.
"From the Australian Open, I had a week at home, but then I went straight to Fed Cup and was there the whole week.
"Fed Cup is a very high-stress environment, and I feel like I'm just about recovered to be here now."