As well as the ongoing Barcelona Open, Nadal is due to make appearances in Hamburg and Rome before the French Open later on May 25th.
The Spaniard feels officials are making it harder for players to play to their full potential.
He said: "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."
Nadal went through into the quarter-finals of the Catalan competition after a 6-4, 6-3 win over Felicano Lopez yesterday (Thursday, May 1st).
The 21-year-old has won 100 of his last 101 matches on clay and is the three-time defending Barcelona Open champion.
Some of the tightly-packed schedule has been put down to the 2008 Olympics in Beijing, where several of the top players will represent their countries.
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