The spectre of the dreaded “m” word — match-fixing — continues to linger over tennis following an extraordinary round-one match in the Monte Carlo Masters this week.

The ATP match in question — which has been the subject of vigorous debate and speculation on online tennis betting forums — was played between Argentina’s Martin Vassallo Arguello and Russia’s Igor Andreev on Tuesday.

During the match, the unusual flow of money for Vassallo Arguello, ranked No.69 in the world, meant he was rated as the favourite even after he had lost the first set, 6-2, to the 21st-ranked Russian.

Andreev opened as a $1.35 favourite on Betfair, the online betting exchange, and around $1.33, or 1/3 in the old terminology, with bookies around the world. Many handicappers had Adreev over the odds to dispose of his opponent — yet money poured in late for the Argentinean.

Despite winning the first set convincingly, Andreev’s odds on Betfair were listed at $2.10, or 10/9, an unbelievable price considering he was the higher-ranked player and had already gone one set ahead.

The second set started with Vassallo Arguello getting an early break to go up 2-0, but Andreev — in defiance of the betting trends — got the upper hand to such an extent that he served for the match at 5-4 and 40-0. With three match points on his serve, Andreev seemingly had the match in the bag.

At this point, Betfair was betting $25.0 or $26.0 on Vassallo Arguello — in layman’s terms, that means the Argentine was available at 25/1 and there were takers at this price even though realistically, in such a dire predicament, he should have been at 250/1 or longer.

But Vassallo Arguello staged a magnificent comeback to stave off those three match points and force the set into a tie-breaker. Andreev served two double-faults in the tie-breaker but still found himself serving with a 5-4 lead. He lost the next three points, however, and the set.

In the third set, Vassallo Arguello barely raised a sweat in clinching it, 6-2, and the match.

Vassallo Arguello is a 29-year-old journeyman without an ATP title to his name. He is perhaps best known for his role in an infamous match in Poland in late 2007 against another Russian, Nikolai Davydenko, which brought the whole match-fixing issue into the spotlight.

That day, Vassallo Arguello was heavily backed to beat world No. 5 Davydenko, even though he lost the first set, again 6-2. The Argentinean eventually won 2-6, 6-3, 2-1 after Davydenko retired, citing a foot injury. Betfair is one of the few wagering houses that pays on incomplete matches.

About $7million was bet on the contest, 10 times the normal amount for a match at that level. The betting exchange eventually voided all bets on the match after studying wagering trends, which were unusually lopsided in favour of Vassallo Arguello winning.

Enraged punters openly spoke of match-fixing. Both players claimed they were innocent. The ATP investigated the match and decided there was no match fixing.

Betfair has paid out on this week’s Monte Carlo result. There may be an innocent explanation for the betting trends, and perhaps the result was no more than a neat coincidence. But one wonders what the ATP made of it, and whether their crack anti-corruption squad will swing into action any time soon.