Christian Horner has told Jean-Eric Vergne and Daniel Ricciardo they have a shot at a Red Bull drive but that they have to achieve it "on merit".
Having been re-signed for a second season, the two Toro Rosso drivers are in pole position to replace Mark Webber at senior team Red Bull in 2014.
However, it they want the Aussie's seat, they need to up their game.
"The objective will be to keep a close eye on them, and at some point we would like to consider them as a driver," Horner told Autosport.
"But they have to achieve that on merit.
"Were we to have a seat available [in 2014], they would have to demonstrate that they have the ability to step up like Sebastian [Vettel] did.
"They have the opportunity do that, but there is no prerequisite that they will be a Red Bull Racing driver.
"It is a great opportunity for them and we will be keeping a close eye on them, but our objective will always be to have the best pairing possible in the cars."
Vergne and Ricciardo, though, are not the only drivers Red Bull are keeping an eye as Horner reckons GP3 driver Antonio Felix da Costa is an "exciting" prospect for the future.
"In Daniel and Jean-Eric, and Felix da Costa, we have got some really exciting young prospects that we keep a close eye on how they develop," he said.
"All three of them are real talents. Ricciardo has done a strong job this year, Jean-Eric in his first year has again done well and shown promise and it is obviously difficult when you are in a car that obviously has got its challenges as well, but they have acquitted themselves well.
"We will run Felix da Costa in the young driver test here. He has done some aerodynamic tests and show runs for us previously, and he has had a tremendous run in [Formula Renault 3.5] since he joined that championship.
"He looks an exciting prospect, but F1 is something totally different."