Although the new engine regulations coming next year do offer fresh opportunity for Red Bull's rivals, Mercedes thinks a closer look at the steps forward the champion team has made in recent months suggest its advantage will not be completely wiped away.
In particular, Brawn thinks that Red Bull has made big gains in its understanding of aerodynamic efficiency to improve its straight-line speed, an area where it had been weak in the past.
"Some of the performance I have observed they have gained in the second half of the year, it looks like performance that will translate into next year," Brawn told AUTOSPORT.
"They suddenly have the car that sometimes tops the speed trap times, and they have never done that in years.
"They have managed to shed some drag off the car, so some of the car's performance in certain areas of the track, if carried over in to next year, will make it very challenging.
"It is a new slate in many ways [in 2014], but I think you don't unlearn things. So things they have modified with this year's car will be applicable for next year."
Red Bull boss Christian Horner says the steps his team have made in the second half of this year have not come at the expense of its 2014 challenge, and any progress it makes from now on will also help it next year.
"While the championship jobs are done this year, whatever we achieve this year we can only benefit from next year," he said.
"Our full focus in Milton Keynes is on the challenges of 2014, but there is still an awful lot we can learn [from the current car].
"The other teams are also involved in a battle for second in the championship. We are out of that and will be able to turn full focus on to 2014."