OK, AO's official announcement (from the link someone posted before : http://www.australianopen.com/en_AU/...705033061.html
) with some words from the man himself, it's better than nothing :
Nadal withdraws from Australian Open
Saturday, 29 December, 2012
By Tennis Australia
Rafael Nadal has withdrawn from next month's Australian Open.
A stomach virus has plagued the Spanish superstar's preparation for the summer as he attempted to rejoin the tour for the first time since a mid-year knee injury.
Ironically, in the end it was the virus, and not the knee, that prompted his decision.
"I am sorry and very sad to announce that I will not play in the Australian Open," the 2009 Australian Open champion said. "My knee is coming along okay, but a stomach virus has left me unable to get ready in time to tackle the rigours of a Grand Slam.
"Because of the virus, I have been unable to get any match practice and simply would not be doing myself or my friends in Australia justice if I went down there so unprepared. You need your body to be at its best for the Australian Open," Nadal said.
"It was a difficult decision and I am extremely disappointed to be missing such a great event. I love coming to Melbourne and playing on Rod Laver Arena before the Australian crowds. It brings out the best in me. It hurts to have to wait another 12 months before I get another chance. In the meantime, the focus is now on desperately trying to get back on the tour."
Nadal was originally due to play his first matches since the surgery in Abu Dhabi followed by an event in Doha. The virus has meant he has had to withdraw from both, thus depriving him of match practice and no doubt playing a large part in his decision to withdraw.
"It is completely understandable and we really feel disappointed for him," Australian Open Tournament Director Craig Tiley said. "But without any match practice and without sufficient lead up time on the practice court, it makes it virtually impossible for him to get his body ready.
"We just hope he gets better quickly and we see him back on the tour as soon as possible. Tennis fans across the world have been missing him. Our Australian Open staff will very much miss him and his team as he is not only a great player, but also a great guy with good people around him,"explained Tiley who has been in regular contact with the Nadal camp in recent weeks.
"We wish Rafa all the best. I am confident we will see him back on the tour soon and back in Australia for 2014, no doubt as one of the contenders for the Norman Brookes Challenge Cup."