Despite an extremely encouraging final test at Barcelona, Mercedes driver Nico Rosberg urges caution, warning that what really matters is when the actual racing begins.

As the German eclipsed his teammate's sensational time this morning, memories of the opening days of the Jerez test were quickly dispelled. The fire that restricted Rosberg's running on the first day was followed by an early crash for his British teammate. Mercedes was back in the headlines, but for all the wrong reasons.

Having appeared to sort its initial reliability issues the team has made steady progress since, culminating in Hamilton's sizzler on Saturday which was itself superseded by Rosberg this morning.

However, taking a break for lunch ahead of the final few hours of pre-season testing, Rosberg was keen to put things in perspective and not get carried away.

"As we all know, we have to be very careful with the results of testing because you just don't know what other people are doing," he told Sky Sports News, "and we know for a fact that our competitors haven't shown their potential yet. So we need to be very careful.

"What I can say is that we have made progress," he continued, "and I am pleased with how the winter has gone. Everything has gone to plan and the reliability has been sorted out. 'Pleased' is probably the best word, but we need to wait and see for Melbourne.

"For sure, I can see that back in the factory things are working well and everything has come together at testing, but performance-wise we still need to wait for Melbourne to see where we are."