Mercedes 'old boy' Nico Rosberg has warned his new team-mate to beware - but not necessarily because he is threatening to match him for pace on the track.

Rosberg and Lewis Hamilton have history, having been team-mates as teenagers in karting, and the German sees no reason not to pick up where they left off, by warning the 2008 world champion to watch his back - and other parts.

Some 13 years ago, the youngsters were notorious for pulling pranks on each other - including Rosberg smearing a well-known heat rub in his team-mate's underpants - and the Chinese Grand Prix winner reckons their relationship is strong enough to withstand a resumption of 'hostilities'.

"It's been good working with Lewis again - the memories have all come flooding back from when we were together before," he was quoted by Britain's Sun newspaper, "It's such a long time ago now, but the memories come back and it feels like being back then. There have been no practical jokes yet, but I am sure there will be time for that."

Both drivers took their turn at the head of the timesheets in pre-season testing and, while neither is predicting great things for the opening round in Australia next weekend, Rosberg sees no reason why they cannot improve on recent Mercedes' results.

"It will be a great challenge to compete against [Hamilton], but that's what I am here for," he said, "He is one of the best drivers in the pit-lane, and I think we can work well together and push the team forward.

"We have to be very careful with testing, [as] you just don't know what other teams are doing. Our competitors might not have shown their potential, but what I can say is that we've made progress and I'm pleased with the way the winter has gone. We had a very difficult time last year, especially with a lot of drop off towards the end of the season. Everything has gone to plan, the reliability has been sorted and it has all come together. As a team, we have progressed."