Qualifier Jamie Hampton knocked out former champion Caroline Wozniacki to earn a place in the final of the Aegon International in Eastbourne.
The American needed nearly three hours to beat the 2009 champion 6-7 (6-8) 7-5 6-3 and reach her first career final.
Hampton, 23, will play Elena Vesnina in Saturday's title decider after the Russian beat Yanina Wickmayer 6-2 6-0.
Should she triumph, Hampton would become the first American to win at Eastbourne since Chanda Rubin in 2003.
Wozniacki had failed to serve out the match after returning from a rain break and the American world number 41, who will play compatriot Sloane Stephens in the first round of Wimbledon, saved two break points at 5-5 in the second set.
"I stuck with it," said Hampton. "Just to get the hold there and stick with it and stay positive was definitely a plus. I'm definitely proud of myself."
In the men's draw, Spain's Feliciano Lopez defeated Ivan Dodig 7-6 (7-3) 6-1 and will meet second seed Gilles Simon, his first round-opponent at Wimbledon next week, in the final.
The Frenchman overcame Italy's Andreas Seppi 6-4 6-3 in one hour and 24 minutes.
"It's funny, funny to play the same guy in three days," said Lopez.
"But this is tennis and sometimes these things can happen. Final is a final. To win the tournament is not easy, so for the moment I take this one obviously."
British pair Colin Fleming and Jonathan Marray lost 3-6 6-3 10-8 to top seeds Alexander Peya and Bruno Soares in the final of the men's doubles.