For the first time in 10 years, Sorana Cirstea will play in the semifinals of a WTA 1000 event after the unseeded Romanian upset No.2 seed and reigning Australian Open champion Aryna Sabalenka in Wednesday's quarterfinals at the Miami Open.

In their first career meeting, Cirstea beat Sabalenka 6-4, 6-4 in the last eight to move into the penultimate round of a tournament of this size for the first time since finishing runner-up to Serena Williams in Toronto in 2013.

It's been a resurgent tournament for 32-year-old Cirstea in more ways that one, as she hasn't dropped a set in five victories. She's also beaten No.5 seed Caroline Garcia this week (after beating her in Indian Wells, too) and former Top 20 players Karolina Muchova and Marketa Vondrousova. 

She took the next step in her second quarterfinal in this Sunshine Double: The 85-minute win over Sabalenka was her first victory over a player ranked in the Top 2 of the WTA rankings. (She was beaten by World No.1 Iga Swiatek in the quarterfinals of the BNP Paribas Open earlier this month.)

"I think I'm a bit speechless," Cirstea said afterwards. "I came out knowing that it's going to be a really tough match. Aryna hits so hard, so I knew I had to hold my ground, and I'm very, very happy with my performance today.

"I guess people like to keep count of the age, the years, the results, but I never do that. I just mind my own business, work hard, do my thing, believe in my game, work with my coach Thomas Johansson -- we just started in December and so far, I think it's going great. 

"I'm not defined by numbers. I'm just trying to keep my head down and work hard."

How the match was won: Cirstea matched Sabalenka's power game for the duration of the contest. She tied Sabalenka with seven aces, and hit just two double faults to Sabalenka's six. Three of them came at the worst possible time for the No.2 seed: on break point.

She also hit 16 winners to a tidy nine unforced errors, as Sabalenka racked up 21 in each category.

Cirstea broke Sabalenka in the first game of each set, but she ended up earning the deciding break later on. She broke for a lead she never relinquished at 4-4 in the opener, and 3-3 in the second set. To win the match, she served out victory from 15-40 down. 

Up next: For a place in the final, Cirstea will face the winner of the evening quarterfinal between two-time Wimbledon champion Petra Kvitova, the No.15 seed, and unseeded Ekaterina Alexandrova.