Jenson Button admits he "doesn't have a clue what's going on" in terms of the pecking order ahead of the first race of the season.
Although Mercedes are once again expected to be the team to beat this year, pre-season testing has thrown up some surprising results with Ferrari, Sauber and Lotus all setting the pace at one point or another.
"I have had time to look at the screens but I haven't got a clue what is going on," Button said. "In terms of who is quick and who isn't, it is really difficult to read.
"I think Mercedes will be quickest, looking at the long runs but Ferrari seems pretty strong, Williams is difficult to read, and Sauber looks good, so good for them – Red Bull too.
"It is tricky, you put the soft tyre on and some gain 1.5secs, others gain four tenths, so it is a bit random. I think it makes it great for the first race and exciting. You could read last year that Mercedes and Williams were quickest, but this year I haven't got a clue so it could be a mixed up field for the first race."
McLaren have had a difficult time so far as the team are yet to come to grips with their new Honda power unit, but Button is confident the MP4-30 will improve once the season gets underway.
"We've had some pretty tough pre-seasons before and we have had it at McLaren," he added. "We had the hoover exhaust I think in 2010 that kept falling apart. Pre-season testing has a lot of the time been very tough but most of the time we can pull it together reasonably well.
"This year you will see, more than ever, the big steps forward, which is exciting, but it needs to start relatively soon."