The Spaniard, who was pipped by Sebastian Vettel to the title last year after finishing just three points behind the German, feels that anyone from five teams could claim victory in the Australian Grand Prix.
"Nobody knows who can win this race, we will just have to wait and see," said Alonso. "These are questions that winter testing didn't answer.
"This year, there is some consistency through the grid and I expect the five top teams to have a little advantage, but of those five teams, it is very difficult to say after winter testing which of them will have the extra two or three tenths which could make them win.
"I think Mercedes, Ferrari, McLaren, Lotus and Red Bull all showed potential at different times during testing, so it's hard to choose. It's very close and difficult to choose one favourite."
The F1 season gets underway in Australia on Sunday.