From 2-2 in the third set against No.8 seed Bojana Jovanovski, No.1 seed Wozniacki won four of the next five games for a 63 36 63 victory. The Dane had lost both of their match-ups this year, so surely relished a measure of revenge.
"It was a very tough match today," Wozniacki said. "I always have tough matches against her. She's a great competitor. The crowd was amazing and really supporting me today. Last time I went this far in the tournament was five years ago. I'm happy to be through to the semifinals."
In that semifinal, Wozniacki will take on third-seeded Sabine Lisicki, a 75 46 60 winner over Karin Knapp. Wozniacki has split her four meetings with Germany's Lisicki, though she was triumphant in both of the hardcourt ones.
"The next round will be tough," Wozniacki said. "Lisicki is playing very strong, serving well and hitting the ball very hard. I need to run a lot of balls down and play fast."
In more good news for Wozniacki, she also clinched an alternate spot at next week's TEB BNP Paribas WTA Championships - Istanbul.
Beck was involved in the most dramatic match of the day, overcoming a match point at 5-4 down in the third set against Katarzyna Piter and going on to a 63 67(3) 76(5) triumph. The three-hour, 12-minute marathon was the longest match of the tournament so far and put Beck into her second WTA semifinal - having also gotten that far in Katowice earlier this year.
As for Voegele, she also matched her best WTA result by beating No.2 seed Sloane Stephens, 63 36 62, for her third three set win this week. The Swiss was down a break at 2-1 in the third set but reeled off five straight games from there to seal the upset. But the day wasn't a total loss for Stephens, as she also booked an Istanbul alternate berth.
Continuing the theme of the day, both doubles matches went to match tie-breaks, with Kristina Barrois and Laura Thorpe upsetting top-seeded Nadia Petrova and Katarina Srebotnik in the semis and Polona Hercog and Lisa Raymond beating second-seeded Kristina Mladenovic and Piter in the quarters.