No.2 seed Simona Halep has been forced to withdraw from the Upper Austria Ladies Linz semifinals due to a left knee injury she sustained during her quarterfinal victory over No.7 seed Jasmine Paolini.

World No.100 Jaqueline Cristian instead advances to her first WTA final. The 23-year-old Romanian is the first lucky loser to reach a WTA final since Coco Gauff - also at Linz exactly two years ago. Gauff won her maiden title here in 2019.

Lucky losers in WTA finals since 2000
Melinda Czink, Canberra 2005 (l. Ana Ivanovic)
CoCo Vandeweghe, Stanford 2012 (l. Serena Williams)
Olga Danilovic, Moscow River Cup 2018 (d. Anastasia Potapova)
Coco Gauff, Linz 2019 (d. Jelena Ostapenko)
Jaqueline Cristian, Linz 2021

Cristian will face No.8 seed Alison Riske, who moved into her 11th career final and second of the season when No.3 seed Danielle Collins retired due to a right shoulder injury after losing the first set 7-5.

"Unfortunately I am not able to play in my semifinal this evening after injuring my knee in my match yesterday," Halep said in a statement. "I would do anything to be able to play, but it is swollen and painful and playing will only make it worse. I want to say a huge thank you to the tournament and fans here at the Upper Austria Ladies Linz for a fantastic week. I hope to be back!"

Halep's streak of winning at least one WTA title every year between 2013 and 2020 has now ended.

While injury prevented the all-Romanian semifinal between Halep and Cristian from happening, the all-American derby between Riske and Collins did at least begin. However, Collins' right shoulder was heavily strapped. Despite taking a 3-1 lead thanks to some rocket returns, the 27-year-old was both error-prone and emotionally flat.

After Riske broke back with a backhand winner, she gradually took control as Collins' level dropped. Having won just four matches this year through the US Open and seen her ranking drop from No.26 at the start of the year to a current No.73, Riske has enjoyed an autumn resurgence. She was runner-up in Portoroz to Paolini in September, and her record since then is 11-5.

"I had a really rocky year," Riske explained. "I was injured for about nine months. I was just healthy starting at Wimbledon, and it's been a slow process coming back - I get emotional thinking about it because it's definitely been a journey."