Red Bull team principal Christian Horner believes that it is "too early" for Jean-Eric Vergne to step up to a seat with his squad.
The Frenchman is on the team's three-man shortlist to replace Mark Webber next year, but Horner has hinted he is no longer a contender for immediate promotion even though he stopped short of ruling him out completely.
Vergne's Toro Rosso team-mate Daniel Ricciardo was invited to test for Red Bull at Silverstone last week, but the Frenchman was not given the same chance.
"Jean-Eric is again demonstrating strong development and potential," said Horner.
"At this stage, it is probably too early for him, which is why we chose to look at Daniel in the test at Silverstone last week."
Horner stressed that he is keen to see Vergne remain in Formula 1 even if he is passed over for the race seat.
As Ricciardo stepped up to an F1 race seat with HRT in mid-2011, compared to Vergne's debut with Toro Rosso at the start of '12, Horner believes the Frenchman is still developing as a driver.
"He deserves a seat in Formula 1 and should he not be successful with the Red Bull seat then it would make logical sense for him to continue with Toro Rosso," said Horner when asked by AUTOSPORT whether he would like to see Vergne have another year with the Red Bull junior team.
"He's six months behind Daniel in terms of F1 experience. He is still learning, still developing.
"We are in the fortunate position that we have got two drivers that have come through the junior programme, that have exemplary junior careers, that have both done fantastic jobs when they have had the chance in a Red Bull car at the young driver tests.
"They are both very capable drivers and both earned their seat in Toro Rosso on merit through the talent they have.
"That is obviously developing as they gather experience."