Coco Vandeweghe booked the first WTA final of her career Saturday with a 6-2, 3-6, 6-2 victory over fifth-seeded Yanina Wickmayer in the WTA hardcourt tournament at Stanford.
The lucky loser from last weekend's qualifying rounds will face either top-seeded defending champion Serena Williams or Romania Sorana Cirstea in the title match.
Vandeweghe got into the main draw after a late player withdrawal and made the most of her opportunity. She beat former world number one Jelena Jankovic in the second round.
The 21-year-old American, coached this week by her mother, will rise to inside the top 75 as a result of her success here, according to the WTA Tour.
She hammered a dozen aces and broke experienced Belgian Wickmayer four times in the match which lasted just over two hours.
At one tense moment Wickmayer drew a warning for swearing.
Vandeweghe said she was furious with herself when she crashed out of qualifying.
"I had a bad tennis day and paid for it," she said. "But once I got into the main draw, I took advantage of my opportunities.
"I stuck with my game plan, I served big and returned well this week. When my game comes together like that I can play well from the baseline.
"I'm just so excited to be in the final."
Vandeweghe's surprise showing this week by far surpassed her previous career bests: quarter-final appearances in her native San Diego and Tokyo two years ago and at Memphis in 2011.
She was the second lucky loser to advance to the WTA semi-finals this season after France's Mathilde Johansson in Fes, Morocco. The last one to reach a final was Hungarian Melinda Czink at Canberra five years ago.
Vandeweghe ran out a winner in the first set, streaking to 5-1 over the 37th-ranked Wickmayer. She closed out the set with a forehand to the corner.
But experienced campaigner Wickmayer responded in the second. She won the final game by saving a pair of break points before claiming it on her second set point.
Vandeweghe regained control in the third, going up a break for 3-1 and breaking again to conclude the upset as Wickmayer double-faulted on her opponent's first match point.