Red Bull's controversial advisor Helmut Marko says that Mark Webber will be expected to play support to Sebastian Vettel as the German aims for his fourth successive title.

Speaking to Bild, Marko said: "Mark knows what we expect of him. For four years, Vettel and Webber have driven together in our team. Sebastian was runner-up once and champion three times. The statistic speaks for itself. There is no reason to think the balance of power will change."

Said to be on the shopping list for a number of teams, despite his age, Webber signed a new one-year deal with Red Bull last July, a move which surprised many, particularly in light of the Australian's numerous comments about perceived bias within the Austrian outfit. Indeed, at the height of the in-team rivalry, having just won the British Grand Prix, Webber sniped 'not bad for a number two' over the team radio, much to the frustration of team boss Christian Horner.

While many already accept that the Australian is the number two, and despite the team's denials, Marko's comments are hardly likely to ease the situation.

Meanwhile, talking to GP International, Webber, who has contested 196 Grands Prix - exactly the same number as Fernando Alonso - admits that as he reaches the end of his F1 career the hardest thing is finding the right time to call it quits.

"I haven't been there yet but it is going to be a very difficult moment, no question about it," he said. "I suppose it's just about getting the timing right - not pulling the plug too early, knowing you have more to give of yourself, or going too long and not being quick enough or struggling to do the things you used to be able to do. That can become an issue as well."