US Open Hires Security, Warns Players Against Tennis Betting

"We're taking this very seriously," USTA Senior Director of Communications Chris Widmaier told the AP. "Do we think there's a problem? Actually, we don't. But we want to make sure we're as equipped and have as much knowledge of this issue as we can. At the end of the day, this goes to the integrity of the game."

Davydenko was involved in a match with Argentine player Martin Vassallo Arguello in Sopot, Poland, when on-line betting sites received about $7 million in wagers, 10 times the usual amount -- most bet on Vassallo Arguello after he'd lost the first set.

"Players are concerned about it, because they certainly don't want it to happen," U.S. Davis Cup captain Patrick McEnroe told the AP. "They would like it to be fully investigated and get to the bottom of it and make sure it doesn't happen again."

The USTA has set up a hotline for players to anonymously provide tips about possible gambling policy violations, and signs describing the Open's gambling policy have been posted in locker rooms, player lounges, training rooms and elsewhere.

The sign reads "REMINDER: The participation in or aiding and abetting, directly or indirectly, of any form of gambling or betting involving tennis is strictly prohibited. The USTA has a zero tolerance policy on gambling or betting involving tennis, and any violation of such policy will result in immediate disciplinary action."