Kirsten Flipkens managed to advance at the San Antonio Open as three of her fellow seeds fell in the first round on Monday.
Flipkens, a runner-up in Monterrey earlier this year, overcame Mariana Duque-Marino 6-3 7-6 (7-4) at the WTA 125K event played on hard courts.
The Belgian seventh seed broke serve five times in her victory, which came in one hour, 40 minutes.
But the news was much worse for fellow seeds Irina-Camelia Begu, Jelena Ostapenko and Nao Hibino.
Second seed Begu went down to Samantha Crawford 2-6 6-1 7-5, while Ostapenko was a 7-5 6-4 loser to Ana Konjuh.
American wildcard Catherine Bellis was too good for Hibino in a 6-3 6-2 win.
Meanwhile, Alison Riske edged Laura Siegemund 7-5 4-6 6-4, Han Xinyun upset Irina Falconi 6-4 1-6 6-3 and Tsvetana Pironkova thrashed Casey Dellacqua 6-1 6-0 in just 43 minutes.