James Allison, the highly-rated F1 engineer who recently left Lotus, is being linked with Red Bull’s future.
When Briton Allison left Lotus, he was most strongly linked with a move to Ferrari.
But Germany’s Auto Motor und Sport reports that, a month after Allison’s departure from Enstone, it is "still not clear" where he is headed.
Correspondents Michael Schmidt and Bianca Leppert said: "Rumours are increasing that maybe he will go to Red Bull.
"Those speculating in the paddock believe that Adrian Newey will stop at the end of 2014.
"The design genius often expresses his frustration with the increasingly restricted regulations, and fears that the new turbo era will make F1 an engine formula."