Mercedes boosted Rosberg's engine before failure

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Nico Rosberg's retirement from yesterday's Italian Grand Prix occurred just after Mercedes turned up the German's power unit in a bid to catch Sebastian Vettel.

Rosberg was gaining on his countryman's Ferrari when a burst of smoke three laps from the end signaled a terminal disorder for his car, dealing a potentially massive blow to the Mercedes driver's 2015 title hopes.

Mercedes motorsport chief Toto Wolff later revealed that Rosberg's engine power had been slightly turned up in the race's closing stages, and a green light given to the driver to up the pace and attempt to catch Vettel.

"We gave it a little push at the end to try to catch Sebastian and this is when it decided to call it a day," Wolff said.

The engine which expired was Rosberg's older-spec Spa unit which had been put back in the car after its new-specification engine had showed signs of weakness in Saturday's free practice session.

"The engine was on its sixth race, so it was very high on miles and we didn't get any warnings," added Wolff.

"We don't know yet whether it is terminally damaged, 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."

Mercedes exploited the entirety of its remaining development token allocation at Monza, supplying both its drivers with the latest generation Mercedes V6 power unit as it looks forward to 2016.

"We brought that phase four engine because we want to understand if the direction of development was the right one. 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."

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