The ATP started its investigation after Davydenko lost to Martin Vassallo Arguello, who was ranked 87th at the time, on Aug. 2, 2007. Vassallo Arguello was ahead 2-6, 6-3, 2-1 when Davydenko retired from the match, saying he had an injured foot.

An online gambling site said some $7 million was bet on the match, with most of the bets on Vassallo Arguello even after Davydenko won the first set. The gambling site said the amount was about 10 times the usual wagered on such a match.

ATP officials on Friday said they found no evidence of wrongdoing by Davydenko or anyone else involved in the match. They said the investigation was closed.

The ATP has threatened a lifetime ban on players found to have fixed a match on the tour.