Shelby Rogers continued her dream run at the Silicon Valley Classic with victory over ninth seed Veronika Kudermetova securing a spot in the final against last year's runner-up Daria Kasatkina who toppled Paula Badosa.
Unseeded 29-year-old American Rogers has knocked off top seed Maria Sakkari along with Amanda Anisimova and 2019 US Open winner Bianca Andreescu on her way to the decider.
Rogers is also yet to drop a set, maintaining that run against the higher-ranked Kudermetova for a 6-3 6-4 victory in one hour and 20 minutes.
The triumph marks Rogers' biggest final in her career and her first on tour in six years.
Rogers, who trailed 2-0 in the second set, broke Kudermetova's serve with her second match point to clinch victory.
Second seed Badosa was bundled out by Kasatkina 6-2 6-4 in 46 minutes in the other semi-final on Saturday.
Badosa did not appear 100 per cent physically throughout the match and Kasatkina capitalised to secure back-to-back finals in San Jose.
The Spaniard had three break points in the decisive game before Kasatkina converted her first match point.
Kaia Kanepi and Liudmila Samsonova both powered their way into the Citi Open final with comfortable victories on Saturday.
Sixth seed Kanepi ruthlessly swept aside Australian Daria Saville 6-3 6-1 in one hour and 13 minutes, moving her closer to her fifth career title. The 37-year-old Estonian blasted 18 winners for the match.
World number 60 Samsonova proved too good for China's Wang Xiyu, winning 6-1 6-1 in one hour and seven minutes. Samsonova's big hitting was a key feature behind her win with four aces and 17 winners.