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When Bianca Andreescu was defeating tennis legend Venus Williams on Friday morning, her father Nicu was glued to the TV at their home in Vaughan, Ont, watching his daughter play.

But her mother Maria, unable to bear the pressure, was tucked away in her bedroom, getting updates from her husband between sets.

"She usually doesn't watch her matches live, but after that she does watch them," Nicu told As It Happens guest host Helen Mann.

Andreescu, 18, stunned the sports world again by beating Williams 6-7(1), 6-1, 6-3 at the ASB Classic in Auckland, New Zealand, to reach her first WTA semifinal.

Sophia Jurksztowicz recaps Missisauga, Ont., teenager Bianca Andreescu's win over Venus Williams at the ASB Classic in Auckland, New Zealand. 2:36

For Nicu, it was a nail-biting experience.

He knows his daughter is a powerful player with a strong dedication to the sport — but he wasn't sure she would prevail over a seasoned champion like Williams.

"I'm still digesting that," he said. "The last few days have been unbelievable. So exciting and unreal."

Andreescu will now take on the tournament's No. 3 seed Su-Wei Hsieh of Taiwan on Saturday morning.

Canadian tennis champion Bianca Andreescu is pictured here as a little girl with her parents. (Submitted by Nicu Andreescu )

But Nicu still remembers signing her up for tennis when she was six years old.

"She was an active kid, running around and all that. We took her to different sports — gymnastics, skating and tennis was one of them," he said.

"When you see a kid at six years old having fun on the court, you don't know what's going to happen later on. But she had the skill."

Her win against Williams came just one day after her 6-4, 6-4 victory on Thursday over world No. 3 Caroline Wozniacki in the Auckland tournament, which is considered a warm-up for the Australian Open that begins in just over a week.

"This was a big moment for her because she dreamed all of her life of playing the big scene, and this was her time to show that she can," Nicu said.

"And she did it very well and backed it up with another victory against Venus."

A few minutes after the big win on Friday, Andreescu was on Skype with her proud parents.

"[She was] so happy, so excited," Nicu said. "She couldn't believe what she just did, and I told her, 'Listen, this is not a dream. This is reality.'"

Written by Sheena Goodyear with files from CBC Sports. Produced by Jeanne Armstrong.