Lewis Hamilton believes Red Bull are going into the season opener in Melbourne next week with an upgrade worth between 0.2 seconds and 0.4 seconds.
Hamilton is favourite to get the 2018 season off to a winning start in Australia, but he is wary of the threat posed by Red Bull as he thinks an upgrade of "some magnitude" is on the way.
"Because we don't bring upgrades at the same time, I think Red Bull will bring something at the first race," Hamilton predicted at a sponsor event in Turin.
"It will be interesting to see. I think Red Bull are the fastest at the moment, potentially.
They have some sort of upgrade coming, of some magnitude, two-to-four tenths (of a second) or something like that. That's what I heard."
Hamilton added that Red Bull can boast having the car that produces the most downforce, but that will be a strength and a weakness throughout the season.
"They always build a car that has lots of downforce. Their maximum downforce has always been more than everyone else's," Hamilton added.
"But that doesn't always work everywhere. Some places where you have longer straights – because they're very slow on the straights, normally, but they're fast through the corners.
"This advantage shifts through the year."