Nadal hasn't played since being knocked out in the second round of the Australian Open by Mackenzie McDonald in late January.
Shortly after that match, it was revealed that he'd torn his iliopsoas muscle in Melbourne and would be out for around two months as a result, missing a number of major tournaments including the sunshine double in the USA.
His initial plan was to return to action at the start of the clay season and that plan looked to be on track when it was reported that he'd be competing in the Monte Carlo Masters, but he's now confirmed that he won't be able to do so.
"I am still not ready to compete at the highest level. I will not be able to play in one of the most important tournaments of my career, Monte Carlo," he said in a statement.
"I am not yet in a position to play with the maximum guarantees and I (will) continue my preparation process, hoping to return soon."
Nadal has won the tournament in Monte Carlo 11 times, more than any other player, and has dominated on clay throughout his career, also claiming 14 French Open titles.
Given his ongoing fitness issues though, it's looking less and less likely that he'll be able to add to that tally at Roland Garros this year.
