Serena Williams fired a warning to Maria Sharapova ahead of their Wimbledon semi-final clash as the world number one admitted she saves her best performances for clashes with her fiercest rival.

Williams and Sharapova meet today in the latest installment of a bitter rivalry that took root on Centre Court in 2004 and still festers more than a decade later.

Sharapova caused one of the great Wimbledon shocks 11 years ago when, aged just 17, she defeated Serena in the final to claim her first Grand Slam title.

The duo's relationship has remained frosty ever since, occasionally turning nasty - as it did when they traded barbs about Sharapova dating Williams' ex-boyfriend Grigor Dimitrov and the American's own relationship with her French coach Patrick Mouratoglou.

But, while Sharapova has collected five Grand Slam titles and built a global brand that makes her the world's highest paid female athlete, the 28-year-old has still been left trailing in Serena's wake and the Russian hasn't come out on top since 2004.

The 33-year-old American has a 17-2 lead in their head-to-head record, winning their last 16 meetings and depriving Sharapova of three major titles in the 2007 and 2015 Australian Open finals and the 2013 French Open final.

Serena has also won all four of her semi-final meetings with Sharapova, defeated the Russian in their previous Wimbledon clash in the last 16 in 2010 and routed her in the 2012 Olympic final at the All England Club. "I love playing Maria. I think she brings out the best in me. I thought we had a wonderful final in Australia. It was very entertaining," said Serena, who remains on course to hold all four major titles at once and is in the hunt to clinch the first calendar Grand Slam since 1988.

"I think it's always a new match. I haven't had great success against her. I would love to change that around. That's how I look at it," Sharapova said.