Heidfeld is surprised by the way Vettel has come to dominate Formula One
In 2007, a then teenage and boy-like Vettel was BMW's Friday driver, supporting racers Heidfeld and Robert Kubica.
"That Sebastian would dominate formula one was not foreseeable at the time," Vettel's German countryman Heidfeld, who earlier this season lost his Renault seat, told the German language Auto Bild.
In 2006 and 2007, before his race career began, Vettel often topped the Friday practice times but he was usually testing with fresher engines and tyres than Heidfeld and Kubica.
"With empty (fuel) tanks he had good times but compared to Robert and I he was too slow," insisted Heidfeld.
"Sebastian did a decent job on the Fridays but his potential was not easy to see. He performed solidly but the car was good for more."
The comments could explain why BMW so helpfully released Vettel into Red Bull's hands for his Toro Rosso debut, with Heidfeld conceding that since then, the now 24-year-old has been "simply unstoppable".
