Mercedes boss Toto Wolff suggests his team are wary of any constructor catching up with the Silver Arrows over the winter break. He fears the rule changes surrounding the aerodynamics on the car could well open up an advantageous loophole that only one team might spot.
The aerodynamic changes are in place to help increase the chances of overtaking by making it easier to follow the car in front. He worries that any team, including Williams, could identify a loophole and challenge Mercedes.
In his interview with motorsport, Wolff highlights the 2009 championship winning Brawn car and believes a similar thing might happen in 2019.
"I think with the rule changes, everything is possible. It is almost like 2009 where Brawn identified the double diffuser. I think there could be teams that have found loopholes, which others didn't spot, that could make the difference," Wolff said.
"So we are taking everybody series: whether it is Ferrari finishing second this year, or Williams finishing 10th. All of them could come with a car that can outperform us."
On route to their fifth world title, the Mercedes team were forced to work harder than ever before. The German says the fact they finished 2018 84 points ahead means nothing in Australia.
"The points go back to zero at the start of every single year. The challenge is going to be bigger than it was this year," Wolff said in Russia ahead of the FIA Prize Gala.