AUCKLAND, New Zealand - Canadian teenager Bianca Andreescu delivered the shock of the early season on Thursday night, as the World No.152 stunned top seed Caroline Wozniacki to reach the quarterfinals of the ASB Classic, 6-4, 6-4.

The 18-year-old qualifier scored her best win in terms of ranking over the World No.3 to reach her second career WTA quarterfinal, where she will face off against another former World No.1 and Grand Slam champion in Venus Williams.

Andreescu previously announced herself on the WTA by reaching the last eight at the Citi Open in Washington, D.C. in 2017, where she upset then-World No.13 Kristina Mladenovic for her previous best win.

"I've pictured myself beating top players like this, and it's really just a dream come true. I know I have the level. [My confidence] skyrocketed like 20 times today. She was No.1 in the world and won a Grand Slam," the Canadian said.

"I just fought until the end. I was in the zone and at one point, I didn't even know the score. I was really pleased with my performance. I tried to stay in the present moment, but at 5-4 in the second set, I really knew I had it then."

Both players received medical treatment over the course of the physical two hour, 14-minute encounter, but it was the teenager's mix of power and variety which ultimately won out in the late evening affair.

Undaunted from the first game, the qualifier was the first to break in the opening set. Andreescu held her first break point as early as the second game, but first came through on her second opportunity after building a 0-40 lead at 2-2. 

The top seed pulled level in a marathon eighth game which went five deuces, where she eventually evened the score at 4-4 on her sixth break point of the game after building her own 0-40 advantage.

Nonetheless, Andreescu held her nerve in the set's late stages, and won four of the next five games to hold a set and a break lead in her first-ever match against a Top 10 player. 

Another key game for the Canadian came in the middle of the second set, as she saved three break points in the match's longest mini-battle - a game which lasted seven deuces - after having seen Wozniacki get back on serve and lead 3-2.

Andreescu held on to stay even, and ultimately powered her way through to the stunning upset by claimin the last three games. 

On the prospect of facing her second Grand Slam champion in as many rounds with the prospect of her first career WTA semifinal on the line, Andreescu said: "I'm just going to go out there like I did today with nothing to lose, just going for my shots and also being patient and aggressive, and have fun. That's the most important thing."