(CNN) -- Five-time champion Venus Williams went out in the opening round of Wimbledon for the first time as she slumped to a 6-1 6-3 loss to Russia's Elena Vesnina.
The former world number one started the match with two double faults and was never able to match the energy of Vesnina, ranked 79 in the world.
Williams came into the match on the back of her toughest year in tennis following a six-month break battling Sjogren's Syndrome, an incurable autoimmune disease that causes chronic fatigue and joint pain.
She was unseeded at the All England Club for the first time since her debut in 1997, having dropped to 58 in the world rankings.
However, Venus quashed talk of retirement following the defeat.
"There's no way I'm going to give up. I love this sport," the American said in her post-match press conference.
"I don't have time to feel sorry for myself. The only thing I can do is be positive."
Williams was the most high-profile casualty so far of an opening day in which most of the women's seeds came through unscathed.
Current world No. 1 Maria Sharapova, fresh from her victory at the French Open earlier this month, began her assault on the title she won as a teenager in 2004 with a 6-2 6-3 win over Australian Anastasia Rodionova.
The No. 3 seed, Agnieszka Radwanska from Poland, wasted little time in wrapping up a 6-3 6-3 win over Slovakia's Magdalena Rybarikova.
Australia's Samantha Stosur, the No. 5 seed, beat Carla Suarez Navarro, from Spain, 6-1 6-3.
China's Li Na, the 2011 French Open champion, quickly wrapped up a 6-3 6-1 win over Ksenia Pervak from Kazakhstan while Sabine Lisicki, the German No. 15 seed, recorded a 6-4 6-2 victory over Petra Martic.
Two-time champion Kim Clijsters, playing in her last Wimbledon, beat former world number one Jelena Jankovic of Serbia 6-2 6-4.
One upset of the afternoon came courtesy of Italian qualifier Carmila Giorgi, who beat compatriot and No. 16 seed Flavia Pennetta 6-4 6-3, while No. 27 seed Daniela Hantuchova was beaten 6-4 7-6 by American Jamie Lee Hampton.