Eight competitors became four as Caroline Wozniacki and Fiona Ferro joined Kiki Bertens and Sorana Cirstea in the semifinals of the Mutua Madrid Open Virtual Pro.

After playing one set to three games in round-robin play, the remaining competitors were extended to a traditional virtual set in Wednesday's quarterfinal round, and Wozniacki continued her scintillating form on the courts of Tennis World Tour to reach the final four in the third quarterfinal of the day.

The former World No.1 and Australian Open champion, who was undefeated in round-robin play, needed just seven minutes to defeat Johanna Konta in a dominant set, 6-0. 

Joined by husband David Lee -- who was celebrating his birthday on Wednesday -- for her victorious post-match interview, Wozniacki revealed that it had been 16 years since she'd logged this many hours playing video games, recalling back to her youth with her brother Patrik. 

And it showed.

"For the first time picking up a joystick in many years..." she trailed off. "It's not called a joystick, is it? What's it called?" 

"A controller!" Lee replied. 

"I called it a computer the other day, and he's like, 'It's not a computer, it's a PlayStation! So I need to get my terminology right, but I'm getting better." 

Wozniacki will face reigning Madrid champion Bertens, who booked her place in the semifinals alongside Cirstea in the first two matches of the day.

Read more: Bertens, Cirstea squeeze into virtual Madrid semifinals

"I played Kiki Bertens the other day in a practice set and she beat me, 3-0," the Dane said. "I think she's at a different level than me, but maybe I've gotten better! Maybe over the past couple of days, I'm playing better now.

"When you play her, it's like playing her in real life: she plays the spins, then she plays the drop shot, then she plays aggressive and has the big serve.

"It's kind of frustrating. I'm excited. I'm excited for the challenge, so I'll see if I can get through this."

In a contrast to Wozniacki's victory, Ferro was given all she could handle by Donna Vekic in the final women's quarterfinal.

The Frenchwoman, who finished atop her round-robin group, and Vekic battled all the way to a tiebreak but clutch serving helped Ferro through.

After Ferro built a 4-1 lead in the tiebreak, Vekic pulled to within a point, but the World No.53 served a pair of aces to keep her challenger at arms' length, seal the victory, 7-6(3), and advance to a meeting with Cirstea.

Ferro, one of the first four competitors who was announced for the charity video-gaming tournament, said that the key to her 4-0 record so far has been a committed effort from her couch. 

"I've been practicing quite a lot: I've been playing for one hour every day for the past two weeks," she said with a laugh.

"We've [Cirstea and I] practiced a few times together and I think that we're about the same level, so it's going to be an interesting match."

The semifinal and final matches will take place on Thursday as the remaining ATP and WTA players will compete for a winner's purse of €150,000 each.