Thirtieth seed Bacsinszky, who needed a bandage applied to her right thigh midway through the first set, looked the more likely victor at that point as she sought to celebrate her 28th birthday by surpassing her semi-final run of 2015.
It didn't help that she tweaked her right thigh in the first set. "I don't know what to expect from her", said Halep, bidding to become just the fifth player to win both the girls' and women's singles titles at Roland Garros.
Trailing by a set and two breaks in the French Open quarterfinals, just one game from defeat, Simona Halep was not exactly full of positive thoughts during a changeover before her opponent tried to serve out the victory. "She was braver. She had more courage".
Pliskova refused to go down without a fight and broke back to trail 4-3 with yet more strong hitting, but Halep was on a mission and regained her advantage courtesy of another stray forehand from the Czech before serving out the match.
The 25-year-old has since dismissed concerns over her fitness and finds herself one win away from a memorable maiden Slam title triumph that would also see her supplant Angelique Kerber at the top.
"Thanks Anabel for helping me", she added.
Logic suggested the steady approach she adopted after losing a topsy-turvy first set in a tiebreak would get the job done for the experienced Swiss, not the white-knuckle rollercoaster tennis Ostapenko was playing.
Bacsinszky's scouting report on Ostapenko, a pal she played doubles with a year ago? Halep has won 11 of her last 12 matches on clay court.
"I mean, when I came here", Ostapenko said, her words spilling out with nary a pause in between, "of course I didn't expect I would be in the final".
Her improvement in the claycourt major bears similarities with the career of Russia's Maria Sharapova, a self-described "cow on ice" on the red dirt who still managed to lift the Suzanne Lenglen Cup twice.
All of her big hitting with a racket that has a white ribbon attached to the frame for good luck gave Garcia fits: The last French player in the tournament made an eye-catching 31 unforced errors, to Pliskova's 13. Kuerten won that title - the first of his three French Opens - on June 8, the day Ostapenko was born.
If she wins, it'll be her first WTA title.
After advancing to the semifinals of the French Open Grand Slam tennis tournament on Tuesday, becoming the first lady tennis player from Latvia to ever do so, Alona Ostapenko said that this achievement is something which is hard to believe, but called tomorrow's match on her birthday as "exciting".
There was not just a grand slam final at stake but also the world number one ranking.
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