LONDON - As the NBA grapples with a betting scandal, tennis must now confront a potential gambling scam of its own.

Officials on Friday were investigating suspicious betting patterns on a match involving top-seeded Nikolay Davydenko of Russia, who retired with an injury against a low-ranked opponent at an ATP tournament in Poland.

In an unprecedented move, British online gambling company Betfair voided all bets Friday placed on Thursday’s second-round match at the Prokom Open in Sopot between the defending champion and No. 4-ranked Davydenko and No. 87-ranked Martin Vassallo Arguello of Argentina.

Betfair said it received about $7 million in bets on the match — 10 times the usual amount — and most of the money was on Arguello to win, even after Davydenko won the first set 6-2.

The tennis probe comes in the wake of the scandal involving former NBA referee Tim Donaghy. He is the target of an FBI investigation for allegedly betting on games, including some he officiated, during the last two seasons. He resigned July 9.

“You try to leave it to the players to play the game the right way,” said Andy Roddick, ranked fifth in the world. “I think we expect that of them. If something’s found that’s shady, I, for one, will be extremely (ticked) off.

“Obviously you want to wait and see it play out, but it’s too bad that it only takes one idiot to ruin things and create a bad story.”

Arguello won the second set 6-3 and was leading 2-1 in the third when the Russian retired. Davydenko said he aggravated a left foot injury in the second set. He received medical attention from a tournament trainer before deciding to quit.

“I don’t think that he (Davydenko) has something to do with this,” Arguello said Friday. “I was playing against him, but he was playing also with an injury, and that’s all that I know about the match, and that’s also what I felt in the match. I felt nothing else.”

Betfair, which has had an agreement with the ATP since 2003 to share information on any irregular betting activity, said it was concerned with the volume of wagers coming in on Arguello from the start.

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“We think the market quite clearly wasn’t fair,” Betfair managing director Mark Davies said. “The prices seemed very odd. 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’s the first time the company has taken such a step in any sport. Davies said Betfair would turn over its betting records for the ATP to investigate.

“The ATP takes issues surrounding gambling extremely seriously,” the men’s tour said in a statement. “We are committed to ensuring our sport remains corruption free and have strict rules in place governing this area.

“In addition we have memorandums of understanding with U.K. and European betting companies that ensures information pertaining to any ATP Tour match that may look suspicious, based upon gambling patterns, is shared with us immediately.”

ATP officials said Friday that Davydenko had left Poland.

“Normally I try to fight to the end but it was very painful and I may have done even more damage by trying to finish the match,” Davydenko said Thursday after the match. “Since the beginning of Monday I’ve had a problem with my left toes. Today that became a problem with my foot.”