The match-fixing scandal engulfing tennis has almost overshadowed the Australian Open, but there could be worse to come for the sport.

Doping might be the next frontier. Just as cycling and athletics have been shaken by performance enhancing drugs, maybe tennis is next.

Until now, it has seemed almost too good to be true. Tennis is one of the most physically demanding sports in the world, alongside perhaps cycling, rowing and multisport.

Cycling has been tainted for decades, with Lance Armstrong's confession confirming what many insiders had known for years. Any potential doping in sports such as rowing and triathlon is more of an unknown but at first glance they lack the financial incentives to have dodgy scientists and chemists involved.

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Tennis is another matter, with huge prize money on offer for the best. And the seasons get longer every year, now stretching into mid-November or even December.

It's seems inconceivable that some wouldn't be tempted by an artificial edge. You still need great skill and mental tenacity - drugs can't turn you into a tennis champion - but they can make you harder to beat.

But few have been caught, despite plenty of rumours. It's well known that one successful male player in the 1990s had large question marks over him, but there was almost no testing back then.

It hasn't got much better, as Roger Federer alluded to last year during the ATP Finals in London.

"I'm always surprised," he said. "I win a tournament, I walk off the court, and it's like, 'Where's the doping guy?' Whenever you make the quarter-finals of a tournament, when the points are greater, the money is greater, you should know that you will be tested."

2014 US Open champion Marin Cilic is one of the few to be sanctioned, after testing positive for a banned stimulant in 2013. He was banned for nine months, eventually serving four.

There is a perception that the world tennis bodies aren't particularly vigilant with testing during or between tournaments. Part of it is funding, with hundreds of tournaments played across the globe, but the perceptions remains that tennis administrators are often happy to look the other way.

There was the shielding of Andre Agassi after he tested positive for crystal meth, and Richard Gasquet managing to convince an ATP investigation that the cocaine found in his system has arrived there inadvertently, passed on from a woman he kissed.