Toto Wolff has admitted he remains worried about engine reliability at Suzuka.
After Lewis Hamilton’s race-ending failure in Malaysia, the otherwise dominant team implemented some quick fixes for the Japanese grand prix.
But boss Wolff admits: "It’s not an easy situation. In one week you are unable to identify the problem in full.
"We are trying to contain it in many ways, but it is no guarantee that we will be ok in the race," he is quoted by Brazil’s UOL.
It is believed one of the measures was not allowing Mercedes drivers to use their special ’qualifying mode’ on Saturday.