Venus Williams couldn't dig herself out of a hole this time and lost to Eugenie Bouchard of Canada 7-6 (6), 2-6, 6-4 at the Family Circle Cup on Thursday.
Williams fought back in each of her first two matches to advance. She seemed to follow the same game-plan in this one, rallying from a set down to win the second set and lead 2-1 in the third.
That's when Bouchard took over, breaking Williams' serve twice in the third set, including the final game.
"She played a lot more consistently than I did," Williams said.
Bouchard finished things off by reaching Williams' drop shot and pushing it into the open court for her first victory over the seven-time Grand Slam champion.
"I've shown to myself how mentally strong I can be," said Bouchard, seeded sixth. "Today was really a mental battle. It was a bit ugly at times and tough on the court, but I fought through it."
Williams was the 2004 Family Circle champion. She reached the semi-finals here last year where she lost to sister Serena, the eventual champion.
Bouchard will next face second-seed Jelena Jankovic, the 2007 Family Circle champion who at No. 8 in world is the highest-ranked player remaining in the tournament. Jankovic defeated Croatia's Ajla Tomljanovic 7-5, 6-1.
Jankovic has reached the Family Circle quarterfinals in six of the past seven seasons. She's been beaten by a Williams sister each of the last two years, falling to Venus in 2012 and to Serena in last year's championship finals.
Jankovic struggled early as the 20-year-old Tomljanovic fought off a set point to tie the opening set at 5-all. Jankovic then won eight of the next nine games to move forward.
"I missed that overhead on my set point, which was kind of frustrating, and we leveled it at 5 5," Jankovic said. "But I was able to stay calm and regroup and finish that set. So that was very important."
Others advancing to the round of eight included third-seed Sara Errani, who outlasted Peng Shuai of China, 7-6 (6), 7-6 (5); Andrea Petkovic, who topped fourth-seeded Sabine Lisicki 6-1, 6-0 and Samantha Stosur, seeded seventh, was beaten by No. 9 seed Lucie Safarova 3-6, 6-4, 6-4.
In an all-German match; Jana Cepelova of Slovakia, who defeated Elena Vesnina of Russia 7-6 (4), 3-6, 6-3; and Daniela Hantuchova of Slovakia, who beat Teliana Pereira of Brazil 6-2, 6-3.
Errani rallied in each of her sets to eliminate Peng, the world's top-ranked doubles player.
For Cepelova, it was her second big victory of this event after knocking off world No. 1 Serena Williams in a stunner on Tuesday.