Jenson Button believes that Mercedes and Williams will be the teams to beat at the start of the 2014 season.
Mercedes-powered teams emerged on top after the three pre-season tests, with Williams's Felipe Massa setting the overall quickest lap time in Bahrain.
"It has been a messy winter for a lot of people in terms of mileage on circuit," the McLaren driver told Sky Sports News.
"The two that you would pick out that look strong and consistent are Mercedes and Williams. In a way it is not good when you are behind certain teams, but I am happy for Frank Williams that they have a competitive car so far this year. I think those are the two teams to beat right now.
"We didn't have our upgrade on the car in testing - we did actually have it on, but we didn't get to run it as we had a few issues - so for the moment we don't really know where we stand. Those two are the teams that I think looked strongest over winter testing, whether that will be the case when we get to Melbourne - it is a very different circuit to Bahrain - we have to wait and see."
Button also downplayed suggestions that Red Bull will start the season off the pace but reckons the reigning champions could struggle to finish races.
"I think you will see them putting in very good laps in qualifying. Whether they can get to the end of a race or not I don't know. For any team, to get to the end of a race is very difficult - especially at the start of the season - and if you do get to the end of the race there are some good points up for grabs.
"I think for the smaller teams it is the best chance to score points - especially the two teams that haven't scored a point in F1 [Marussia and Caterham]. It is going to be a tough start to the season, reliability is important, but to win you just don't need reliability, you need a competitive car and an intelligent team behind you that really understands what it takes to win a race."