Sharapova, fresh from winning the French Open and reclaiming the world No 1 ranking, dropped only one point in the opening four games against Australia's Anastasia Rodionova although she was eventually forced to engage second gear in 6-2 6-3 victory.

Maria Sharapova of Russia hits a return to Anastasia Rodionova of Australia during their women's singles tennis match at the Wimbledon tennis championships in London, June 25, 2012. [Photo/Agencies]

The Russian will face Bulgarian Tsvetana Pironkova in the second round - a dangerous opponent who reached the semifinals in 2010 and the quarterfinals last year.

"The first one's always tricky," Sharapova, the darling of Wimbledon 2004, told reporters. "To go out there after not competing for a couple weeks, the transition from clay to grass, I thought I started off the match really well."

Maria Sharapova of Russia hits a return to Anastasia Rodionova of Australia during their women's singles tennis match at the Wimbledon tennis championships in London June 25, 2012. [Photo/Agencies]

On paper Williams' defeat by Vesnina represented a shock, although those present on the bowl-like Court Two were watching a pale imitation of the woman who has graced the tournament since appearing with her braids, beads and raw talent in 1997.

Venus Williams of the US hits a return to Elena Vesnina of Russia during their women's singles tennis match at the Wimbledon tennis championships in London, June 25, 2012. [Photo/Agencies]

The American, who since losing that debut match to Poland's Magdalena Grzybowska had never experienced an opening round defeat here, was 5-0 down in a flash and never recovered in front of a sympathetic Court Two crowd, some of whom had queued from the early hours of the morning to grab a ticket for the more intimate show court.

"I feel like I'm a great player but I have to deal with circumstances that other people don't have to deal with in the sport," Williams, who finished 2011 outside the world's top 100 after battling with injury and Sjogren's syndrome, a little-known disorder that causes fatigue and joint pain.

"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," added the former world number one who only returned to action after a seven-month lay-off in March.

"I'm as tough as nails."