Coulthard says Toro Rosso spell showed Vettel is a team leader

Mercedes team boss Ross Brawn said last week that the test of Vettel's true skill will come when he does not have the fastest car in Formula 1, unlike over the past two years.

"For Sebastian, what will come now, which will be an interesting phase of his career, will be when he has not got the best car," said Brawn. "It will be interesting to see Sebastian's role, Sebastian's influence, Sebastian's position when perhaps he does not have the best car, he has to make it the best car, and has to create the best car."

Coulthard, however, believes Vettel already showed he can lead a less successful team in 2008, when he gave Toro Rosso its maiden win at the Italian Grand Prix.

"I have tremendous respect for Ross Brawn, but what Seb was able to achieve at Toro Rosso already showed he is a team leader," said Coulthard during a media event at Red Bull's factory.

"Whoever thought they would win a grand prix? But he was able to put it on pole in the wet and then win the grand prix, which was truly remarkable. He's already done it, culminating in two championships.

"What I do think is valid is how he handles the inevitable disappointment when his car isn't for whatever reason the best."

Coulthard also thinks that Ferrari driver Fernando Alonso could be a good benchmark for Vettel if he gets a competitive car.

"Alonso won two championships when Michael [Schumacher] was in his prime. Since then the car has not quite been there but once it is he will be very hard to beat. All you can do, if you look at the history of the sport, you need a reference to another driver.

"Mark Webber is no slouch, he's a fantastic driver and Seb has largely dominated him this year, so that has to be acknowledged.

"I don't think we're getting carried away saying how good he could be - he's fought for the win when he didn't have to, his pass on Lewis Hamilton at Korea, that was ballsy stuff."