Five-time champion Venus Williams insisted she would return to Wimbledon despite crashing out of the tournament in round one for the first time since her 1997 debut.
The 32-year-old American, who is fighting an ongoing battle against illness, was bundled out in straight sets by Russian Elena Vesnina, who claimed a fine 6-1 6-3 success on Court Two.
Williams' only previous experience of a first-round singles loss at Wimbledon came as a 17-year-old in 1997 when she was defeated by Polish player Magdalena Grzybowska.
Williams is down at 58th in the world rankings, with Sjogren's syndrome, an auto-immune disease which has had a major effect on her health, having kept her out of the game between last summer's US Open and the WTA tournament at Miami in March.
Asked in her press conference whether she would be back at Wimbledon next year, Williams said: "I'm planning on it."
She added: "I feel like I'm a great player. I am a great player.
"I'm up for challenges.
"There's no way I'm just going to give up. That's just not me.
"I'm tough, let me tell you, tough as nails.
"The only thing I can do is be positive.
"I love this sport. I feel I can play well and I'm not going to give up on that."
Vesnina could hardly believe her achievement, with the 25-year-old dancing a jig of joy and all smiles after securing a second-round clash with number three seed Agnieszka Radwanska,who dispatched Magdalena Rybarikova 6-3 6-3
Williams fell 5-0 behind in the opening set, against a player Briton Heather Watson beat in the French Open first round last month.
She slowly improved but could not find a way to turn the match around.
Williams had game point for 3-3 in the second set but frittered it away by overshooting the baseline and Vesnina broke.
It was soon 5-2 as Vesnina held serve, and although Williams had a love game straight afterwards it was only delaying her opponent's charge.
There were no such struggles for tournament favourite Maria Sharapova who started her bid for back-to-back grand slam wins with a first-round victory over Anastasia Rodionova.
The 25-year-old Russian flirted with brilliance in a 6-2 6-3 win, racing into a five-game lead and dropping just three points in the process, before having to adapt a more hardworking approach to see the game out.
Her form and post-match words will send warning signs to her rivals, though, with Sharapova not intent on letting her recent French Open success distract her.
"The first one is always tricky," she said. "I thought I started off the match really well.
"It was a nice feeling to be back on Centre Court. It's such a special place for me.
"I'm still very humble and appreciative for what I have. I still believe I can achieve a lot more. That's what drives me and gets me up in the morning."
Sharapova now meets Tsvetana Pironkova, a three-set victor over Vesna Dolonc on Court Four, with Petra Cetkovska following her immediately on court with a routine 6-4 6-2 success over Vania King.
Kim Clijsters was also victorious in what is her final Wimbledon.
She saw off Jelena Jankovic 6-2 6-4 and then declared that despite having barely any game time over recent months due to injury, she feels capable of making her mark.
"I believe that if I'm healthy and playing my best tennis that I can beat a lot of top players here," she said.
"It's a matter of trying to achieve that every match."
Number three seed Agnieszka Radwanska was largely untroubled as she got past Magdalena Rybarikova in straight sets, while the same went for fifth seed Sam Stosur against Carla Suarez Navarro.
Li Na, looking for an impressive showing after a first-round exit at the French Open, dropped just four games in beating Ksenia Pervak.
Jamie Lee Hampton saw off Daniela Hantuchova while the eighth seed, Angelique Kerber, and the 20th, Nadia Petrova, were victorious on Court 18 against Lucie Hradecka and Maria Elena Camerin respectively.
Sorana Cirstea beat Pauline Parmentier and Eleni Daniilidou retired against Bojana Jovanovski.
Also successful today were Alice Hlavackova, Arantxa Rus, Anna Tatishvili, Sloane Stephens, Stephanie Foretz Gacon and Timea Babos, while 16th seed Flavia Pennetta was beaten by Camila Girogi in straight sets and Sabine Lisicki dropped just six games in seeing off Petra Martic.
Completing the list of victors on Monday were Silvia Soler-Espinosa, Su-Wei Hsieh, Ekaterina Makarova, Shuai Peng, Mathilde Johansson, Ayumi Morita and the 17th seed Maria Kirilenko.
The 12th seed Vera Zvonareva, at one set all with Mona Barthel, will resume on Tuesday after bad light brought their tussles to a halt.
