Madison Keys became the latest top-10 seed to bow out of Wimbledon after a dramatic defeat by world number 120 Evgeniya Rodina.
Keys, who was the US Open runner-up last year, crashed out 7-5 5-7 6-4 to the Russian on a baking hot Court Three.
The 23-year-old American threatened a remarkable comeback in the third-round contest, coming from a set and 4-0 down to force a decider.
But Rodina, 29, held her nerve to reach the last 16 at a grand slam for the first time.
Keys' defeat means that seven of the women's top 10 at this year's championships have already been knocked out.
Defending champion Garbine Muguruza, Caroline Wozniacki, Sloane Stephens, Elina Svitolina, Caroline Garcia and Petra Kvitova have fallen by the wayside during the first week, and now Keys joins the list.
Ekaterina Makarova, who knocked out second seed Wozniacki on Wednesday, continued her fine tournament with a 4-6 6-4 6-1 win over Czech Lucie Safarova.