Gauff youngest WTA semifinalist since 2004

What started with a little luck is now a historic display of precocious skill. 

Fifteen-year-old Coco Gauff lost in the final round of qualifying at the Linz Open, a WTA International event in Austria. But a last-minute withdrawal from Maria Sakkari saw her make the main draw as a lucky loser.

Three wins later, the American is now the youngest WTA semifinalist since Nicole Vaidisova in 2004. She's also secured her breakthrough into the WTA's Top 100; when the rankings are updated on Monday, she will be the only player under the age of 18 in that exclusive club.

On Friday, Gauff took out top seed and world No. 8 Kiki Bertens of the Netherlands, 7-6, 6-4, to notch her first career WTA Top-10 win. She was never broken in the quarterfinal clash, saving the only two break points she faced in the match—both in her first service game of set two. It was Gauff's third meeting with a current Top-10 player, after losses to Simona Halep at Wimbledon and Naomi Osaka at the US Open earlier this year.

She had previously got past Stefanie Voegele of Switzerland and then Kateryna Kozlova of Ukraine in the first two rounds in Linz.

Gauff will now take on Germany's Andrea Petkovic, currently ranked No. 75, in Saturday's semifinals. Should she reach the final, she will face either No. 8 seed Ekaterina Alexandra (the only seed remaining in the draw) or 2017 French Open champ Jelena Ostapenko.