"What's going to happen, I can't predict, but anything is possible."
However, the world No.9 said he would use the Miami Open in late March as a gauge to assess his injury return, not the year's opening Grand Slam.
"Looking overall, the first two weeks of the season have been positive for me," Nadal said. "[But] let me play for three months and then we will see where I am.
"I can go to Australia and I can play very well, but at the same time ... you never know what's going on.
"Probably after Miami, that's going to be a good moment to analyse what's going on and to see where I am."
In the end, Canadian Raonic fired down 23 aces to the Spaniard's four and blasted 50 winners to Nadal's 19 in their heavyweight Brisbane quarter-final.
"Well, I lost against third in the world in a very close match," Nadal said. "I have already played six matches this year, so that's a positive for me - winning five, losing the sixth.
"And the result was so close, so that's a positive, because that means that my mind was ready to keep fighting until the end."
But Nadal tried to keep a lid on his Australian Open aspirations.
"You never can feel confident," he said. "Last year, I felt that I was ready. I had a good week of practice in Melbourne and then I lost in the first round.
"So you never know and you can't predict."
Former Wimbledon runner-up Raonic takes on seventh seed Grigor Dimitrov of Bulgaria and Japan's world No.5 Kei Nishikori plays US Open champion Stan Wawrinka in today's Brisbane men's semi-finals.