Wimbledon 2015: Jelena Jankovic confident after beating champ Petra Kvitova
Jelena Jankovic, Dinara Safina and Caroline Wozniacki were all undistinguished world number ones, each failing to win a grand slam either before, during or after their reigns at the top.
Safina has since retired due to back problems, with Jankovic and Wozniacki still seeking that elusive breakthrough.
In 30-year-old Jankovic's case, the third-round win over defending champion Petra Kvitova showed she still has the game to tackle the best in the game. Now to show it more consistently.
"I'm overwhelmed, I'm so excited," said Jankovic, the 28th seed.
"Playing on grass is not easy for me and she was playing great tennis. But after I won the second set, I kept on trying.
"To beat a two-time Wimbledon champion is amazing and beating her gives me a lot of confidence for the rest of the tournament."
Jankovic now meets Agnieszka Radwanska, who despatched Casey Dellacqua of Australia 6-1 6-4.
The Pole, who was runner-up in 2012 and is seeded 13, needed just 63 minutes to reach the last 16. She said after her win that playing on grass makes everything easier for her style of play. "The surface makes a huge difference. Everything is just easier for me."
Caroline Wozniacki, who has yet to win a slam, got one round nearer achieving that with a 6-2 6-2 defeat of Camila Giorgi.