Upsets happen in tennis. All the time. It’s why a lot of sharp bettors swear by the sport as a moneymaker.

A recent upset at Poland’s Prokom Open, however, resulted in winning wagers going unpaid and a re-emerging headache for the ATP tour. It also sheds light on how European and U.S. governments differ in their approach when faced with the first whiffs of a betting scandal. 

Nikolay Davydenko, ranked No. 4 in the world, lost to No. 87 Martin Vassallo Arguello after withdrawing from the match in the third set, claiming a foot injury. Davydenko won the first set 6-2, lost the second 3-6 and was losing 1-2 in the third before quitting.

U.K. betting exchange BetFair was flooded with Arguello money before and during the match and subsequently raised its post-match concerns with the ATP.

“One punter who followed the match reported that tournament favorite Davydenko's pre-match odds drifted to  (the equivalent of +130 in American-style betting),” reports the Evening Standard’s website ThisisLondon.co.uk. “Even though he was facing a player who stood 87th in the tour rankings.”

The pre-match line move, however, paled in comparison to the in-game action BetFair received.

"The odds seemed very strange given what was happening in the match,” BetFair’s managing director MarkDavis told Today, a popular morning TV show in the U.K. “At the beginning of the match if you bet a pound on Davydenko you would get 20 (pence) back.

"He then won the first set, but if you put a pound on him at that point, a set up, it would have paid out £4.30; considerably more even though he was winning, so it does look strange.”

So strange, in fact, that successful Arguello bettors are still waiting on their winnings from BetFair.

''The prices seemed very odd,” Davis later told reporters. “As a result, in the interest of fairness and integrity and in consultation with the ATP, we have decided to void the market and return all stakes to (bettors).''

It should be noted that BetFair is a betting exchange rather than a sportsbook, where bettors and bet-takers on both sides of a match dictate the line rather than in-house oddsmakers.

The fact that an injury may have played a factor in the heavy Arguello action will make tennis bettors recall other allegations of impropriety over the last five years. The Evening Standard suggests that loose lips could, indeed, sink sportsbooks’ ships once players’ injury discussions filter out of the locker room.

The ATP is wary of any bettor taking advantage of such injury information and has an agreement with U.K. and European sportsbooks to investigate large wagers on matches with suspicious betting patterns.

The ATP’s biggest nightmare, of course, would be one of its own players betting on himself to lose. No surprise, then, that the organization sent a memo to players and coaches warning against match-fixing earlier this year.

Davydenko's agent has since denied any wrongdoing on behalf of his client. 

"Neither Nikolay nor his coach nor me nor anybody out of our entourage has been involved in this," Eckhard Oehms told the Associated Press on Saturday.

"He's a very plain, open person," Oehms continued. "He just couldn't get what this is."
 
"He hasn't won a tournament this year ... He had to defend a lot of points in Sopot and he has no other tournaments to make up for it. So, he personally has no reason whatsoever for foul play. He's desperate to win."

Paranoia over crooked betting is so high even governments are piping up. London’s The Guardian reports that British Sports Minister Gerry Sutcliffe responded to the recent tennis betting scandal with threats of jail sentences.

“When the Gambling Act comes into force on September 1, it will mark the start of a new zero-tolerance approach to betting cheats,” Sutcliffe told the paper. “It will introduce a new two-year jail sentence and give the Gambling Commission powers over betting fines for the first time, including the ability to suspend and void bets and a new requirement on bookmakers to share information with sport."

That’s all well and good. Bettors like you and me, who don’t have inside information, want to believe that the market is on the up-and-up.

But BetFair’s suspicion and the British government’s fist-shaking doesn’t prove that anything crooked went down in Poland, right?

Davydenko reached the Round of 16 at Wimbledon just over a month ago, but that was on grass, the fastest of surfaces. He’d played three subsequent tourneys on clay before the Prokom Open and lost to his first opponent in all of them. His vanquishers on the much slower surface were ranked Nos. 57, 81 and 50 in the world, not far off Arguello’s ranking.

The Prokom Open is also played on clay.

Combine Davydenko’s poor form on clay with a possible leak of info on his sore foot and it’s possible, possible, that loads of tennis bettors saw fantastic value in Arguello against a struggling and hobbled opponent.

The in-match betting, however, is troubling. I like upsets as much as the next guy, but if I watch the tournament’s top-ranked player win the first set of a best-two-of-three 6-2, there’s no chance I’m laying coin on the underdog as the second set starts.

But tons of bettors were doing just that. Way too many for a relatively low-profile ATP tournament, according to BetFair.

That raises the possibility of a potentially massive gambling scandal on both sides of the Atlantic. European investigators, however, will undoubtedly resolve things before their American counterparts resolve the Tim Donaghy / NBA scandal. Legalized and regulated gambling overseas results in the measures noted above and an overall openness that protects regular Joe Bettors.

Over here? It’s hard to keep track of who’s responsible for betting irregularities when the government keeps gambling in backrooms and out of sight.