The world number three has not played since losing to Czech Lukas Rosol in the second round at Wimbledon in June and has been suffering from a partial tear of the patella tendon and an inflammation of the Hoffa's fat pad in his left knee.
The 26-year-old former world number one, who was unable to defend his Olympic title in London and had to withdraw from the U.S. Open, said on Monday he would be out for another two months.
"We have completely ruled out surgery," , Spanish tennis federation doctor Angel Ruiz-Cotorro said.
"During the next month we'll be doing training with a lot of physiotherapy combined with hydrotherapy and laser and we'll see how he progresses," he added.
"We believe that within two months the tendon will be in what we consider a normal state.
"In a month's time, if the tests and his progress are positive, he can get back to work on the court.
"But that's not the main goal, that is for the tendon to recover with the same strength it had."
Ruiz-Cotorro said Nadal's injury would not necessarily plague him for the rest of his career and he was aware of similar cases where the tendon had completely healed.
"It won't necessarily drag on, this injury," he said.
"He wants to play when he can do so in perfect condition and not just for one tournament but to have continuity.
"When they tell you you can't play such important tournaments you are never pleased but now he is keen to recover and return as soon as possible."