Toto Wolff has admitted that Mercedes's two drivers may continue to struggle with their race starts this year.
Just eight points separate Nico Rosberg from Lewis Hamilton, and the latter has warned that a troublesome clutch system could actually decide the outcome over the final six races.
"We have always had starts in the last few races that were not ideal," Mercedes team boss Wolff admitted to German broadcaster Sky.
"It's our Achilles heel and we will not be able to solve it this year.
"We have to change the architecture of the clutch for the coming year, because at the moment of course it is a problem for us."
After early clutch trouble in 2016, Wolff had said that parent company Daimler would be engaged for help.
However, he now says: "We don't know what [the problem] is - whether it's the design or the construction or whether it's the difficulty for the drivers to operate. There are so many factors involved."
Next up on the calendar is the Malaysian Grand Prix this weekend.
