The head of Russian tennis says he is certain that Nikolay Davydenko has had no involvement in match fixing.
The ATP insists it is not investigating Davydenko himself
Davydenko's defeat by Martin Vassallo Arguello at last August's Sopot Open is being investigated by the ATP because of irregular betting patterns.
"There is not sufficient evidence to make any allegations against him," Russian tennis chief Shamil Tarpishchev told BBC Sport.
"I've known him for many years - he's not a gambler let alone a match-fixer."
Last week Davydenko told BBC Sport he believed the ATP, the governing body of men's tennis, was victimising him because they wanted him out of the top 10.
The world number four said: "Maybe they just found one tennis player who they want to remove from the world's top 10?
Corruption in Russian tennis is concocted by those who are eager to indulge in wishful thinking
Head of the Russian tennis federation
"Maybe there is someone below me in the rankings who is more popular and they want to increase his popularity?"
The 26-year-old said he was also frustrated that the investigation into the match had taken so long.
Tarpishchev agreed, and said he did not think Davydenko had been treated fairly by the ATP.
Yet Etienne de Villiers, the chief executive of the ATP, emphasised that his organisation was not investigating either player and added: "We said this is about an irregular betting pattern and we need to get to the bottom of it."
Tarpishchev is also angry about comments made by Larry Scott, the head of women's tennis, last week.
Scott said he suspected that organised criminals, and even the Russian mafia, could be involved in trying to fix matches.
"We need facts rather that suspicions to make such a statement," Tarpishchev said.
"As I understand, Mr Scott hasn't cited a single true fact to prove his point of view. Therefore I think he was more guided by emotions than by real facts.
"There is no corruption in Russian tennis. Corruption in Russian tennis is concocted by those who are eager to indulge in wishful thinking."