Dr Helmut Marko has dented Sebastien Buemi's hopes of one day moving to Red Bull Racing by insisting the Swiss is not a potential race winner.
Marko, in charge of the energy drink company's driver programme, justified the decision to oust both Buemi and his 21-year-old teammate Jaime Alguersuari from the rookie team Toro Rosso during an interview with La Gazzetta dello Sport.
"They had their chance for three years and that's enough to evaluate the development of a driver," said the Austrian.
"We didn't see in them the possibility for more. They are grand prix drivers, but not enough for what we want, which is to have grand prix winners."
Buemi, who has been appointed Red Bull's reserve driver, told a Swiss newspaper late last week he hoped to use the role as a springboard to possibly replacing Mark Webber in 2013.
Spaniard Alguersuari on the other hand is still looking for a job for 2012.