Rosberg's engine faces further investigation

Mercedes elected to use all its engine development tokens for an upgrade of its power unit at Monza as it eyed early development work for 2016.

However, a cooling system issue on Rosberg's power unit caused a problem in final practice and he was forced to revert to the previous specification engine. That unit then failed in the closing stages of the race.

Mercedes motorsport boss Toto Wolff said the engine would now be investigated at its Brixworth headquarters to find out if it can be used again.

If not, Rosberg will have to switch to his fourth power unit for Singapore.

"We don't know yet whether it is terminally damaged," said Wolff. "And to make the point – it wasn't an engine specific failure we had. It was a leak in the cooling system which led to the engine to fail."

When asked if there had been any early warning prior to Rosberg's failure, Wolff said: "The engine was on its sixth race, so it was very high on miles. We didn't get any warnings, no.

"We gave it a little push to try to catch up Sebastian [Vettel] and this is when it decided to call it a day."

Early work better

Although the engine situation was not ideal for Mercedes, Wolff said that bringing in its bold upgrade strategy was essential for it to make the progress it wants for 2016.

"We brought that phase four engine because we want to understand if the direction of development was the right one," he said. "It was a bit of a risky call.

"We saw what happened to Nico and that was the result of that engine. The reliability runs were on quite a high mileage but they weren't finished yet, so in hindsight we lost a car and Nico lost valuable points.

"But this is a very competitive championship. It is going to be one next year and the earlier you can understand which direction you need to go, the better it is."