Rafael Nadal has criticised tennis chiefs, saying the crowded European tennis calendar is being "destroyed".
The Spaniard is currently playing in Barcelona and takes on compatriot Feliciano Lopez on Thursday.
But having won the Monte Carlo Masters on Sunday, and with events in Rome and Hamburg to come over the next two weeks, Nadal says his form will suffer.
"These people are destroying Europe and Europe used to be the foundation of the tour," said Nadal.
"I think it's completely impossible to play at one's best level for all four tournaments - Monte Carlo, Barcelona, Rome and Hamburg.
"You just have to accept this situation, all the players will be the same, they will not be able to play at their high level for all four, I think it's totally impossible."
The ATP has made several changes to the calendar in 2008 to accommodate the Olympic Games in August.
The result is that the clay-court season has become especially congested ahead of this month's French Open.
Monte Carlo, Rome and Hamburg are all Masters Series events, which automatically count towards a player's ranking.
"I think that when a player loses in the first round or pulls out and they get criticised, the tournament should ring these people (the ATP) and tell them that it is their fault.
"I have some email conversations with these people but it is true that they end up doing what they like and I am getting tired of it all."
American James Blake added: "The Olympics is such a unique experience that we need to make arrangements for but the calendar is too packed and maybe we should take out the Davis Cup in Olympic years.
"You'll see how many matches (Nadal) plays this clay-court season, how many matches guys like (Roger) Federer, (Andy)Roddick, (Novak) Djokovic and myself play throughout the entire year."It's probably too much to expect a player to have a lengthy career. It makes it very difficult."