Serena Williams at the WTA Championships in Istanbul.

Serena Williams at the WTA Championships in Istanbul. Photo: AFP

Serena Williams knows that Lance Armstrong was a champion cyclist, now stripped of his Tour de France titles, and a cancer survivor and charity worker. Maria Sharapova is not a cycling fan, but is also aware of Armstrong's achievements, and illness. And the rest.

"It's unfortunate, but I guess it happens," the Russian said of Armstrong's fall from grace.

So what of the anti-doping procedures in tennis?

Consider that Petr Korda was an Australian Open champion who tested positive to steroids, current pro Wayne Odesnik faced charges in Brisbane for illegally importing human growth hormone, and several past and present players, including current world No.7 Sara Errani, have been linked with Armstrong-connected medico Luis Garcia del Moral.

Recreational drugs? See Andre Agassi, Mats Wilander, Jennifer Capriati, Martina Hingis, etc.

So, is drug testing stringent enough in tennis?

Williams: "Stringent enough is putting it mildly. People show up at my house at five in the morning trying to test me. You never know when they come. Yeah, I get tested a lot. I don't know about the other players, but for me it's a pretty intense system, and I know a lot of the players feel the same way."

Sharapova: "Are they enough? Considering I landed from New York and my first day back at home I got a wake-up call at 6am, I think that's enough," she said, laughing. "Yep, knocking on my door. I was like, 'thank you - welcome home'."

But she supports the system, despite the occasional awkwardness.

"I know it seems difficult to have to give one hour every single day, but I usually have my hour somewhere in the middle of the night because I'm not going to be anywhere but in my bed," said Sharapova, the second seed at the year-end WTA Championships in Istanbul.

"If they come get me up they can wait and I can wait until I have to go to the bathroom. It's the most awkward thing when they knock on your door at six in the morning and you're walking around in your robe and your dog is going, 'What is going on? Who are these strangers?'

"It's just a really bizarre situation."