"I'm really happy. It's that I'm at a loss for words. I went out on the court knowing it was going to be a tough match and it was a little unexpected to be honest," Cirstea said, according to Reuters.
Cirstea hasn't dropped a set and is the only remaining unseeded player in the tournament. When Cirstea served for the match, she fell into a 0-30 deficit against Australian Open winner Sabalenka, who in the previous major tournament in Indian Wells was in the final.
She then saved two break balls and was able to win when Belarusian Sabalenka knocked out a forehand.
"Aryna hits so hard and I knew I had to keep my groundstrokes.
32-year-old Cirstea has been 21st in the rankings at its best and that was ten years ago.