Among all the talk of a U.S. Open roof and whether Serena Williams will break through the calendar Grand Slam ceiling, 19-year-old Estonian Anett Kontaveit has found herself in the clouds.

Kontaveit, the world's 152nd- ranked player who barged her way into the Open by winning three straight matches in the qualifying tournament last week, yesterday pulled off a third consecutive upset in the main draw.

Kontaveit knocked off 25-year-old American Madison Brengle, ranked 47th, 6-2, 3-6, 6-0, after having eliminated No. 60 Casey Dellacqua of Australia and No. 31 Anastasia Pavlyuchenkova of Russia. Next, Kontaveit will face two-time Open champ Venus Williams.

"I haven't got my head around that I'm in the fourth round," Kontaveit said. "I mean, my first goal was to qualify. Then, you never know what kind of draw you're going to get. I could've played Venus in the first round, or Serena in the first round. So I didn't really have, like, a big goal. Just try to do my best every single round."

Only one player with a lower ranking is still alive in either the men's or women's draw -- No. 154 Shelby Rogers of Charleston, South Carolina, also a qualifier. And Rogers' chances of joining Kontaveit in the fourth round are slim; she will play No. 2 seed Simona Halep in a third-round match Saturday night.

Likely, Kontaveit said, her three qualifying matches sharpened her game and confidence. And experience in the Open's junior tournament "definitely makes it more comfortable. You've seen the place, you've been on the courts, you've hung around."

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But this? A fourth-rounder vs. Venus Williams? "Not what I was expecting," she said.

Kontaveit took up the sport at 6, because her mother is a tennis coach. Against Mom, she said, "We never actually played points. I guess she didn't like running."