The No.7-seeded Halep was the first to move through to the final four, dropping a 52-minute, 62 60 decision on No.4 seed Sara Errani. It was a stark contrast to the pair's only previous meeting - Errani lost just one game against Halep en route to a 61 60 victory at Miami just under a year ago.
"It was a difficult match. I couldn't prepare very well because I'm not 100% - I have an injury - and I can't run very well on the court," Halep said. "But I was very strong mentally and just wanted to focus on every point. She's a great player and comes back very well and runs very well, so I knew it was important to just stay aggressive and finish the points, and the match, as soon as I could."
Halep was asked to elaborate on the injury. "It's in my Achilles," she commented. "I feel pain, and when I'm running I feel it. I hope it isn't a very dangerous injury and that it will get better soon."
And on getting revenge on Errani? "Yes, I can say that, because I didn't forget the match in Miami," she said. "She beat me so fast, so quickly - but this time I changed tactics and was more aggressive."
Halep is now on a four-match win streak against Top 10 players - and has won six of her last nine.
Next up for her is the No.2-seeded Radwanska, who cruised past Yanina Wickmayer at night, 62 61. Wickmayer had beaten Radwanska in their very first career meeting four years ago, but Radwanska has now won all four of their meetings since in straight sets - and this one in just 64 minutes.
"I've had easy scores until now, but it doesn't mean I've had easy matches," Radwanska said. "I played great tennis, especially today, and Yanina was a tough opponent - every time we play I have to really push myself 100% to beat her. I think I just played really, really good tennis out there tonight.
"I cannot complain about anything."
Radwanska leads Halep in their head-to-head series, 3-1, but the one Halep win came in their last meeting at Rome last spring - and that got the ball rolling on the aforementioned six-of-last-nine stat.
"I've played Simona a few times, the last time in Rome on clay, so the conditions will be a bit different this time," Radwanska said. "But she had a really great season last year, having some good results, and I saw her playing a couple of matches here as well. Today she was playing unbelievable.
"It's for sure going to be a tough match, but it's a semifinal, and everyone's playing well."