Toto Wolff says it is 'worrying' to see Ferrari's rapid form during the Malaysian Grand Prix, adding that it should be a wake-up call for the team to react.

Sebastian Vettel's win for Ferrari at Sepang is just the fourth time in the last 21 races that Mercedes has been defeated, though this is arguably the first time it has been defeated in a straight fight since the introduction of the new regulations in 2014.

Whilst Ferrari itself is aware the unusually hot conditions arguably played into its hands due to the car's ability to preserve its tyres, Wolff - whilst congratulating the Scuderia for its faultless performance - admits it is proof Mercedes cannot afford to rest on its laurels.

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"It is worrying," he said. "In these circumstances here with the high temperatures, they were able to go at a faster pace over long runs than us. We need to analyse why that was the case and it clearly shows it's not going to be an easy one.

"We've had completely different conditions here. One of the explanations today is the extremely high ambient and tarmac temperatures. We've probably gone a bit too aggressive on setups which pushed us into a direction of a three stop, which was pretty clear with all the algorithms."

Coming two weeks' after Wolff said he was impressed with Ferrari's step forward, he admits he wasn't expecting its rate of development to take it to victory so soon.

"We didn't expect them to catch us this quickly. We were pretty dominant in Melbourne, but we are always a little bit sceptical about our own advantage. That we've been caught up by a Ferrari in two weeks, that they beat us fair and square on the track, is a bit of a surprise, but equally a bit of a wake up call, which is good for us.

"We just need to analyse where in the next couple of days where we want wrong, what we need to improve, whether we need to bring any developments forward, put them on the car quicker, what we are doing about engine number two... Definitely, we need to increase the pace of our development."