According to one Red Bull insider, David Coulthard’s DTM career "could have been the shortest of all time".
The Scottish veteran has tested a Mercedes C-class car of the German touring car series and is linked with a race seat in 2010.
But Germany’s Auto Motor und Sport says the move may have been soured by the diminishing relationship between Mercedes and Red Bull.
Reports this week have the two brands at loggerheads over F1 engines, and 38-year-old Coulthard is still a regular in the Red Bull garages at grands prix.
The magazine said Red Bull mogul Dietrich Mateschitz is also unhappy about Mercedes’ new deal to promote the Monster energy drink in formula one.
Emulating Red Bull’s tactic of using alliances with extreme sports to promote its brand, Monster is now seen as the market leader’s major competitor.