Hungarian Timea Babos took the scalp of fourth seed Ana Ivanovic in their late-night second-round clash at the Monterrey Open.
19-year-old Babos has dropped out of the world's top 100 on the back of poor results this year, sliding from 64th to 123rd after a host of early tournament exits.
This was a match to savour, though, for the teenager as she took a close first set before Serbian player Ivanovic levelled the match, and then held her nerve in the decider to come through a 7-5 3-6 6-2 winner.
In only her second quarter-final of the season, Babos will by strange coincidence face the player who beat her in the first of those, Romanian Monica Niculescu.
Niculescu ousted Babos in Florianopolis last month, going on to win the tournament, and she knocked out Belgian sixth seed Yanina Wickmayer 6-4 3-6 6-1 to reach the last eight.
Seeds Urszula Radwanska, Anastasia Pavlyuchenkova and Ayumi Morita all won their second-round games.