Helmut Marko says that in the event that anything should happen at Red Bull Racing, the team would immediately call in Toro Rosso's Carlos Sainz.
The comment suggests that Red Bull's expected third driver Pierre Gasly would not be called upon by the outfit in the event of a force majeure.
The fact that several teams courted Sainz last year and over the winter, such as Renault and Mercedes, has made Red Bull realize the outstanding value of the Spaniard who is kept in Toro Rosso's bull pen.
"We have a long term contract with Carlos and the situation at Mercedes shows how important it is to have reserve drivers," Marko told Spanish daily AS.
"Sainz is clearly our reserve driver in case anything happens at Red Bull Racing."
While Marko believes the Faenza-based outfit should provide a car worthy of Sainz' talent, the Austrian insisted that his skills would not have been better served by Renault.
"Toro Rosso has to achieve better results so we have the target of fifth place for them in 2017.
"With a good designer like James Key they have the potential, and we see it as positive that both drivers - Sainz and Daniil Kvyat - are staying because that provides stability.
"They are a good mid-field team and what Carlos was offered by Renault was no better than that, or worse," Marko concluded.
GALLERY: F1 drivers' wives and girlfriends
Keep up to date with all the F1 news via Facebook and Twitter
