Five-time Wimbledon champion Venus Williams suffered her worst All England Club defeat in 15 years on Monday, but top seeds Novak Djokovic and Maria Sharapova powered into the second round.
Williams lost 6-1, 6-3 to 79th-ranked Russian Elena Vesnina in what was the 32-year-old's first opening round loss since her 1997 debut.
But the former world number one -- the champion in 2000, 2001, 2005, 2007 and 2008 -- believes she can still compete at the top level despite her ranking having slipped to 58 after a six-month absence fighting serious illness.
"There's no way I will give up just because I have had a hard time in the first four or five tournaments back. That's not me," said a fiesty Williams at a post-match news conference.
When asked if she will play at Wimbledon in 2013, she was adamant.
"Sure," she said. "I feel like I am a great player who has had to deal with exceptional circumstances. I don't have time to feel negative. It doesn't feel good. I am as tough as nails, I don't have time to be sorry for myself."
The American star arrived at Wimbledon, where she was unseeded for the first time since her 1997 debut, short of confidence having been sidelined with Sjogern's Syndrome, a disease which causes joint pain and fatigue.
Monday's defeat was just her fourth loss at the first round stage of a Grand Slam against 52 wins.
Vesnina, who had lost in the first round of nine of her last 10 Grand Slam appearances, will face Polish third seed Agnieszka Radwanska for a place in the last 32.
Top seed Djokovic, opening business on Centre Court, reached the second round with a 6-3, 6-3, 6-1 win over Spanish veteran Juan Carlos Ferrero.
Djokovic, playing for the first time since his French Open final defeat to Rafael Nadal, will next face either America's Ryan Harrison or Lu Yen-Hsun of Taiwan.
The 25-year-old had seen his hopes of becoming just the third man to hold all four Grand Slam titles at once shattered by his defeat at the hands of Nadal in Paris.
Sharapova, who completed a career Grand Slam with victory at the French Open, was second-up on Centre Court and eased past Australia's Anastasia Rodionova 6-2, 6-3.
Sharapova, the 2004 champion, has now beaten Rodionova five times in five meetings without dropping a set.
The 25-year-old world number one will face Bulgaria's Tsvetana Pironkova, who reached the semi-finals in 2010, in the last 64.
"It's always difficult when you have had no matches on grass before Wimbledon," said Sharapova. "It can be tricky but you just focus on what you have to do."
US Open champion Samantha Stosur and ex-French Open winner Li Na also reached the second round.
Stosur, the fifth-seeded Australian, had the honour of being the first woman into the last 64, cruising past Spain's 40th-ranked Carla Suarez Navarro 6-1, 6-3.
The 28-year-old Stosur, who was a semi-finalist at the French Open earlier this month, has never got beyond the third round at the All England Club and had been beaten in the first round in 2010 and 2011.
Her win earned her a second round match with Arantxa Rus of the Netherlands.
Chinese 11th seed Li Na, the 2011 French Open winner, enjoyed an emphatic 6-3, 6-1 victory over Ksenia Pervak of Kazakhstan.
Li had beaten Pervak by the same score at the same stage of the Australian Open and next faces Romania's Sorana Cirstea.
Radwanska, a quarter-finalist in 2008 and 2009, made the second round with a 6-3, 6-3 win over Slovakia's Magdalena Rybarikova.
Sabine Lisicki, the 15th seed and a semi-finalist last year, enjoyed a 6-4, 6-2 win over Croatia's Petra Martic.
Flavia Pennetta, the 16th seed, was knocked out by compatriot and qualifier Camila Giorgi, 6-4, 6-3.
Later Monday, six-time champion Federer begins his campaign against Spanish left-hander Albert Ramos.
Unseeded Kim Clijsters, a four-time Grand Slam title winner, who will retire after the US Open, meets fellow former world number one Jelena Jankovic, the 18th seed.