Sergey Ovchinnikov, who coached Russia's women's volleyball team at the London Olympics, has been found hanged in his hotel room in Croatia.
The 43-year-old is believed to have committed suicide, although a police spokesman told state news agency Hina that the circumstances surrounding his death are still being investigated.
Ovchinnikov was staying in the Croatian town of Porec for a pre-season training camp with Dynamo Moscow, having returned to club duties after Russia's disappointing performance at the Olympics.
The national women's side, who won back-to-back world titles in 2006 and 2010, had been expected to challenge for the gold medal but lost in the quarter-finals to Brazil.
Russian media blamed Ovchinnikov and his lack of international experience for the defeat, prompting speculation the 43-year-old killed himself over the scrutiny of his coaching.
Vladimir Alekno, who guided Russia's men's volleyball team to London gold, said Ovchinnikov was hurt by the loss to the eventual gold medallists.
"I could see his reaction after that loss," Alekno was quoted as saying by local media.
"He took it very personally. He was very hard on himself, probably blamed himself for not winning that match."
However, Ovchinnikov's agent Yegor Nozdrin said he believed his client was having personal problems.
"There was absolutely no reason for what happened from a sporting point of view," he told Sovietsky Sport.
"He was thinking of continuing his coaching career, discussing his future plans before leaving for Croatia. I think it had to do with some personal things in his life."
Ex-head coach Vladimir Kuzyutkin was quoted as telling the Russian News Service that he believed Ovchinnikov killed himself over the Olympics, saying: "This is so stupid. I don't know why he couldn't cope with it."
Kuzyutkin later denied making the comments.
Ovchinnikov is survived by his wife and two children.