"As my team and doctors say, the safest thing to do is to do things well and this virus has delayed my plans of playing these weeks. I will have to wait until the Acapulco tournament to compete again although I could consider to play before at any other ATP event," said Nadal, in a statement on his Facebook page.
"My knee is much better and the rehabilitation process has gone well as predicted by the doctors, but this virus didn't allow me to practice this past week and therefore I am sorry to announce that I will not play in Doha and the Australian Open, as we had initially scheduled."
Nadal is currently ranked No. 4, and has not played a match since losing to Lukas Rosol in the Round of 64 at Wimbledon in June.
Nadal won the Australian Open in 2009, and lost to Novak Djokovic in the final in 2012.