World No 4 Barbora Krejcikova saved seven match points to edge an epic third set tie break against Anett Kontaveit and storm into the Sydney Classic final on Friday.
The French Open champion looked out for the count when she lost the first set to love against the seventh-ranked Estonian, but re-focused to take the match into a deciding third.
It could have gone either way in a high-quality toe-to-toe encounter from two of last year's most improved players, who signalled they will be a real threat at next week's Australian Open.
But it was Krejcikova who eventually triumphed 0-6, 6-4, 7-6 (14/12) after 2 hours and 30 minutes on her fifth match point, after saving seven, to prevent Kontaveit from reaching her fourth final in a row.
She will play either in-form 26th-ranked Russian Daria Kasatkina or Spain's world No 9 Paula Badosa in Saturday's decider.
"I just planned to fight more and try and stay in the match," Krejcikova said on her comeback from a first set bagel.
"I felt that at some point I would get my chances and it was important to convert them. I had to find a plan B and I'm really happy that I did. It was a wonderful match."
Both players were newcomers to the season-ending WTA Finals last year, where they had their only previous meeting when the Estonian won in straight sets en route to the final.
That victory was part of Kontaveit's stellar year-end run, where she won 28 of her last 32 matches.