Erika Andreeva delivered a second-round upset at the Abierto GNP Seguros WTA 500 event, taking out No.1 seed Danielle Collins 1-6, 6-3, 6-3 in 1 hour and 51 minutes.

Monterrey: Scores | Order of Play | Draws

Must See

The result is Andreeva's first career win over a Top 20 player, and moves the 20-year-old into the quarterfinals of a Hologic WTA Tour event for the first time.

"Every time I play this [level] of opponent I try not to think about [their ranking], because it puts more pressure on me," said Andreeva afterwards. "Can I do it? And, I have to take all my opportunities I get. But this time I was like, OK, I just hit the yellow ball and I don't care who I play."

Andreeva, the older sister of 17-year-old Roland Garros semifinalist Mirra Andreeva, had to recover from a devastating blitz from Collins in the one-sided opening set. The American, playing for the first time since her quarterfinal run at the Paris Olympic Games, fired 12 winners, repeatedly teeing off on return. Andreeva was unable to tally a single winner of her own.

But the World No.89 managed to adjust to Collins's pace in the second set, and was able to bring the match back to her own terms with clever use of angles and deft drop shots. Opening up the court with quick changes of direction, Andreeva found 12 winners over the second and third sets, while an off-balance Collins racked up 27 unforced errors compared to the 10 she had committed in the opener.

"Honestly, the first set just went so fast," said Andreeva. "She did also amazing hitting. I pushed myself to be more aggressive, and pushed more on the first shots to make her less comfortable."

The remainder of Tuesday's matches in Monterrey saw the first round of the tournament completed. No.6 seed Linda Noskova needed just 49 minutes to race past qualifier Anna Danilina 6-0, 6-1; the 19-year-old dropped nine points in the first set, and did not face a game point through the first 11 games of the match.

No.9 seed Magdalena Frech had a somewhat tougher time against Nadia Podoroska, advancing 6-4, 4-6, 6-4 in 2 hours and 37 minutes. The Pole led 3-1 in the second set, but had to battle back from 4-1 down in the third. No.7 seed Yuan Yue was also taken the distance by qualifier Aleksandra Krunic, eventually moving on 4-6, 6-2, 6-3.

Frech battles back from 4-1 in decider to best Podoroska in Monterrey