Romanian Simona Halep showed the full extent of her defensive skills to beat Karolina Pliskova 6-4 3-6 6-3 and reach her second French Open final on Thursday.
The third seed, who will become world number one if she defeats Latvia's Jelena Ostapenko in Saturday's showdown, benefited from her opponent's unforced errors in the first set before Pliskova rediscovered her touch.
Overwhelmed by Pliskova's power in the second set, Halep regained the momentum in the decider, frustrating her second-seeded opponent with her ability to soak up punishment.
She ended the contest on her first match point with an unreturnable serve to reach her second Roland Garros final after losing the first one to Maria Sharapova in 2014.
In the earlier semifinal, Ostapenko blazed a trail into the final with a 7-6(4) 3-6 6-3 victory over Swiss Timea Bacsinszky in a battle of the birthday girls on Thursday.
On the day she turned 20 the free-swinging world number 47 launched a fusillade of winners to become the first unseeded player to reach the women's singles final at Roland Garros since Mima Jausovec lost to Chris Evert in 1983.
A match of wildly fluctuating fortunes, with barely a service hold in sight, appeared to be slipping away from Ostapenko when she lost four games in a row to lose the second set against Bacsinszky, who was hoping to celebrate her 28th birthday by going one better than her semifinal run in 2015.
But Ostapenko played fearlessly in the decider and pounded away a 50th clean winner to become the first Latvian player to reach a grand slam final.