On Tennis/Johnny Watterson:At this year's Wimbledon Roger Federer said it would be easy to do but he had not heard of anyone doing it.

The American Justin Gimelstob has warned it may be going undetected and echoed Federer by adding, "It's 100 per cent possible and I have my suspicions."

Those comments were offered in response to questions about the current elephant in the corner of professional tennis - match fixing.

The Russian Nikolay Davydenko has recently been under suspicion and is being investigated by the Association of Tennis Professionals (ATP), the body that runs men's tennis.

The result of the investigation could cost tennis its clean image.

While the issue of drugs has popped up intermittently down the years, there has been insufficient evidence to sully tennis's wholesome reputation. But things may be about to change.

Two years ago the Georgian Irakli Labadze, ranked 47th in the world, was accused of throwing a match with the unseeded Julian Knowle in the Raiffeisen Grand Prix in the Austrian town of St Pölten. Labadze, it was said, conspired with a professional gambler to make money by deliberately losing.

Needless to say, tennis authorities twitched nervously amid growing fears some players and their associates could be cleaning up on gambling websites by betting on matches the results of which they knew in advance.

Labadze fell under suspicion after he unexpectedly lost in the first round at St Pölten and his gambling friend Martin Fuehrer won 17,000 after betting 10,000 on Labadze losing.

When Fuehrer went to collect his winnings, the bookmaker, Cashpoint, refused to pay out, claiming Fuehrer had spoken to Labadze about the contest beforehand and knew the Georgian would lose.

So, fast forward to recent weeks when an otherwise uneventful second-round match in Poland involving Davydenko, then ranked four in the world, attracted much attention.

Davydenko was playing the 87-ranked Martin Vassallo Arguello when betting spiked on a London-based website.

More than 5 million, at least three times the amount usually bet on such a match, was laid, and there was big money on the underdog. It raised red flags with officials at Betfair.com, who alerted ATP officials.

In the match Davydenko was one-all in sets and led two-one in the third before retiring with a foot injury. Suspicions soared, and the following day Betfair voided all bets on the match.

The ATP are investigating Davydenko, who has maintained his innocence. He has said an MRI proves he has a stress fracture in his left foot. A theory rife in the tennis world is that someone knew of Davydenko's injury and spread the word.

And do you know something? It seems reasonable that is exactly what happened: that someone - physio, doctor, wife, manager - was simply aware of the extent of Davydenko's injury and took advantage.

Indolence prevented yours truly from seriously considering a bet at this year's Wimbledon, despite the urge to hit the online sites after a fourth-round match between Serena Williams and Daniela Hantuchova.

For a time during the match, Williams was barely able to run after injuring a calf muscle, but she battled to an incredible 6-2, 6-7 (2-7), 6-2 win.

Williams dropped the second set but the pair resumed after a rain break and Hantuchova failed to take advantage as the heavily strapped Williams went for big serves and winners at every opportunity.

Serena was supposed to play a second-round doubles match with her sister Venus in the following days. But given how protective of their bodies both Williamses are - they have suffered down the years with injury - it was a sure thing they would default in their doubles match, against the eighth seeds, Annabel Medina Garriques and Virginia Ruano Pascual, to give Serena the best chance possible of advancing in the singles.

The American pair had won their first-round match 6-1, 6-3 against the former Irish Federation Cup player Claire Curran and Britain's Anne Keothavong, and though unseeded, they were likely candidates to win the doubles outright, having done so before.

The astute gambler, having seen Serena injure herself, could have logically bet on line that the Williams sisters would not advance beyond the second round in the doubles.

As it happened, Serena did not publicise the fact they were defaulting from the doubles until her press conference, which came some hours after the victory over Hantuchova.

And so it may have been with Davydenko: simply that some alert punter, perhaps an acquaintance or even another player, picked up on the Russian's difficulties prior to the match and spread the word that sparked off the betting. Or maybe it's as Gimelstob believes and the ATP fear: tennis results are just too easy to tamper with.