Watson's task looks far from elementary when you consider Williams has won 20 Grand Slams, has been of top of the world rankings for more than two years and a sixth Wimbledon title would see her close in on a second Serena Slam of all four majors in the same calendar year.
In the men's draw, seventh seed Milos Raonic faces Australian bad-boy Nick Kyrgios after sending down the third-fastest serve in Wimbledon history in his last match.
Former champions Novak Djokovic and Maria Sharapova are in action again on what is expected to be another sunny day in SW19.
Defending champion Novak Djokovic faces Bernard Tomic on Centre Court.
Kyrgios has provoked negative headlines in his opening two matches, with the 20-year-old's on-court histrionics not well received down under.
While his temperament has been called into question, his raw talent has not and he loves the grass at Wimbledon.
Last year, ranked 144th, he became the first man outside the top 100 to beat a world number one at a Grand Slam since 1992 when he knocked out Rafael Nadal.
He went on to lose to Raonic in a hard-fought quarter-final so will be seeking revenge when they meet again on court two.
Kyrgios believes his 24-year-old opponent's booming serve is "the best in the game".
