Serena not a fan of new doping regulations

The new rules mean players must let drug-testers know their whereabouts for a period of one hour on every day of the week – a measure which Nadal said makes players feel "like a criminal". The previous version of the rule obliged players to keep anti-doping authorities informed of their whereabouts on only five days a week.

Britain's Andy Murray described the measures as "draconian", and Williams, speaking after her 6-1, 6-2 victory over Karolina Sprem in the second round of the Paris Open on Thursday, agreed. "It's too much," she said. "If I want to go on vacation to Barbados for one day, I shouldn't have to say I'm going to Barbados. "I'm always complaining to my agents. I never tell people where I am, because I like to do my own thing."

The World Anti-Doping Agency (WADA) rule operates on a 'three strikes and out' basis over a period of 18 months, and Williams revealed that she had already fallen foul of the legislation. "One time, I was out at dinner and someone turned up at my house to test me. I think I might even have got a strike. "It's bizarre. I can't run home from dinner and get tested. It's very invasive." Despite her reservations, though, Williams accepts that WADA's stance helps safeguard the sport's reputation. "I think tennis is the purest sport out there," she said. "We won't have problems in tennis that we have in other sports, so it's definitely a pure sport and that's the only upside to it."

Players who miss three surprise tests in 18 months face a possible two-year ban. American Mike Bryan has missed two already due to a flat tire in his car and a late breakfast out and fears against committing a third strike. Roger Federer, while not a huge fan of the system, has not gone so far as to criticise it like his colleagues.