British number two Heather Watson secured her best win of 2016 as she beat Caroline Wozniacki 7-5 6-4 in the Monterrey Open quarter-finals.
Watson broke the former world number one in the penultimate game of the first set in Mexico and sealed victory when the Dane hit a forehand wide.
The 23-year-old plays France's Caroline Garcia in Saturday's semi-final.
Earlier, fellow Britain Johanna Konta lost 6-3 6-7 (2-7) 6-1 to world number 73 Kirsten Flipkens.
Watson has slipped down the rankings to number 84 this year and Saturday's encounter with Garcia will be her first semi-final since winning in Hobart in January 2015.
"I thought I played very well," said Watson. "I needed to against Caroline because she's a great player - and I had to fight to the end because I knew she would."
Konta, ranked 27th in the world, was a set and a break down but broke back to level the second set at 5-5 before winning it in the tie-break.
However, she won only one more game as Belgium's Flipkens reached the last four.
Elsewhere, British number three Naomi Broady lost 6-4 6-3 to sixth seed Eugenie Bouchard in the Malaysian Open semi-finals.