Five times Wimbledon champion Venus Williams has crashed out of the tournament on the opening day, beaten 6-1 6-3 by Russian Elena Vesnina.
It was the former world number one's earliest loss at Wimbledon since she went out in the first round on her debut in 1997.
Williams, 32, returned to the WTA tour in March, seven months after being diagnosed with auto-immune illness Sjogren's Syndrome.
She never recovered from a terrible start against doubles specialist Vesnina and lasted just 75 minutes on Court Two in a match she littered with unforced errors.
Almost every shot looked an effort for the American, and at changeovers she plodded slowly to and from her chair.
After the match, she took umbrage at suggestions that she was struggling and might now think about retirement.
"There is no way I am just going to sit out just because I had a hard time the first five or six freaking tournaments back, that is just not me," she said.
Williams will stay on for the doubles with sister Serena. The pair hope to defend their title at the London Olympic tournament next month.
World number one and top seed Maria Sharapova made a brisk start to her campaign with a 6-2 6-3 win over the Australian Anastasia Rodionova.
Djokovic, Federer untroubled
In the men's tournament, defending champion Novak Djokovic barely broke stride in the opening match on Centre Court.
Djokovic cleared a potentially tricky first hurdle with a crushing win over a former French Open champion, the Spaniard Juan Carlos Ferrero 6-3 6-3 6-1.
Fellow Serb Janko Tipsarevic also made it through to the second round with a straight sets win over Argentina's David Nalbandian, who was defaulted from the final of last week's Queens Club tournament in London.
And six-times champion Roger Federer opened his programme with an emphatic win over 43rd-ranked Spaniard Albert Ramos 6-1 6-1 6-1.