The Rossoneri custodian ruptured ligaments in his right knee during last weekend's 5-1 win over Siena.
"It is the worst injury setback of my career," he told Telelombardia.
"But I am keeping calm and I accept the situation. I am already looking ahead and hoping to recover as quickly as possible.
"When I return to action I will have to win back my place in the starting 11 so I need to get back stronger than ever.
"For now Milan fans shouldn't worry because Nelson Dida is playing like the great 'keeper he was before."