Jan.3 (GMM) There is pressure on Mark Webber to perform in 2013, Red Bull's Dr Helmut Marko insists.
"Mark knows what we expect of him," Austrian Marko - the main link between team owner Dietrich Mateschitz and the Christian Horner-led F1 team in Milton-Keynes - told Germany's Sport Bild.
Now 36, he has been with Red Bull since 2007.
"For four years Vettel and Webber have driven together in our team," Marko said. "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," he added.
If Webber is not retained beyond 2013, he could retire.
He says finding the right time to go is important.
"I haven't been there yet but it is going to be a very difficult moment, no question about it," Webber is quoted by GP International magazine.
"Now I have a lot of wisdom it's about dropping that into your whole skill set and performing better.
"But there comes a point where even that's not enough to keep you at the front. And that's when you need to stop," he said.