Five-time champion Venus Williams lost in the first round of Wimbledon for the first time in 15 years today but insisted the tournament has not seen the last of her.

The 32-year-old has been battling the auto-immune disease Sjogren's syndrome and was a shadow of her former self in losing 6-1 6-3 to Russia's Elena Vesnina.

Williams, now ranked 58th, returned to the WTA Tour in March after six months away with the aim of qualifying for the singles tournament at the Olympics, which she achieved.

She will therefore return to Wimbledon next month for the London Games, and asked whether she would be here next year too, she said: "I'm planning on it."

Williams bristled when one journalist described her as struggling in the press conference, and she is confident that, given time, she can rediscover her form.

The American said: "I feel like I am a great player. I am a great player. Unfortunately, I've had to deal with circumstances that people don't normally have to deal with in this sport.

"But I can't be discouraged by that, so I'm up for challenges. I have great tennis in me. I just need the opportunity.

"There's no way I'm just going to sit down and give up just because I have a hard time the first five or six freaking tournaments back. That's just not me."

Third seed Agnieszka Radwanska had little trouble against Magdalena Rybarikova, winning 6-3 6-3, while fifth seed and US Open champion Sam Stosur saw off Carla Suarez Navarro 6-1 6-3.

Last year's French Open winner Li Na began her campaign with a 6-3 6-1 win over Ksenia Pervak and Germany's Sabine Lisicki, a semi-finalist here 12 months ago, beat Croatian Petra Martic 6-4 6-2.

But 16th seed Flavia Pennetta did go out, the Italian losing 6-4 6-3 to countrywomen Camila Giorgi, who came through qualifying.