Ostapenko then hit a winning forehand to secure her place in the final, prompting the crowd to sing "happy birthday" as she celebrated the biggest win of her career so far. "I love to play here, I love you guys, you're fantastic, thanks for coming to support me".
- Ostapenko took the first set 7-6 (4).
However, Ostapenko played fearlessly in the decider and pounded away a 50th clean victor to become the first Latvian player to reach a Grand Slam final.
Halep will become world number one if she defeats her polar opposite Ostapenko, as well as the first Romanian woman to lift the Suzanne Lenglen Cup since Virginia Ruzici in 1978. I'm looking forward to playing it.
Halep, the No. 3 seed, broke Pliskova in the third game of the opening set to take an early 2-1 lead. "The exciting thing is that if she wins the title, she becomes the WTA world's No. 1", said Pierce.
Halep was thankful still to be in the tournament after her remarkable recovery from a set and 5-1 down against Elina Svitolina in the quarter-finals.
Bacsinszky was left to ponder what might have been after losing in the last four of the Paris major for the second time, but took the positives from an impressive run. Halep goes into the final as favorite against the tournament's revelation, 20-years old Latvian Jelena Ostapenko. She proved herself by beating the second seed on Thursday, too.
Halep was moving well from the start and saved a couple of break points in the next game before holding with a crisp forehand down the line.
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The Portugal global finished 12 goals behind Lionel Messi in the La Liga scoring charts, but ended the season as a champion. The first half ended as a 1-1 stalemate following Cristiano Ronaldo's opener and Mario Mandzukic's stunning equalizer.
Remarkably, it was also the birthday of Ostapenko's opponent Timea Bacsinszky, who turned 28, but it was the world number 47 who came out on top 7-6 (7/4) 3-6 6-3.
Timea Bacsinszky of Switzerland is facing unseeded Jelena Ostapenko of Latvia on Court Philippe Chatrier.
The contest was tight, Ostapenko winning 106 points to Bacsinszky's 105, but even that did not spoil the mood of the Swiss, who was obviously disappointed but dejected. The matchup presents a lot of interesting variables, as Ostapenko has already proven that she can play against highly-ranked players.
The Latvian is the first teenager to reach the French Open semi-finals since 2007 when Serbia's Ana Ivanovic pulled off the feat.
But just when the storm appeared to have blown over Ostapenko, who knocked over former runner-up Sam Stosur and former world number one Caroline Wozniacki en route to the semis, hit another purple patch to roar home from 3-3. Kuerten won that title - the first of his three French Opens - on June 8, the day Ostapenko was born. Halep has won 11 of her last 12 matches on clay court.
The first set seemed to fit the pattern many expected.
Pliskova struck the ball ferociously, but paid the price for 55 unforced errors after being put under huge pressure by a relentless and vibrant Halep.