Red Bull boss Christian Horner has said Carlos Sainz is a "safety net" should Daniel Ricciardo decide to leave the team next year.
Unlike team-mate Max Verstappen, who recently signed an extension through to the end of 2020 with Red Bull, Ricciardo is playing the waiting game with seats potentially becoming available at Mercedes and Ferrari for the 2019 campaign onward.
And while Ricciardo continues to assess his options, Horner has said that stance was the reason why Sainz was only allowed to join Renault on a loan deal.
"That’s why we kept Carlos Sainz on loan, that’s why we have options around us," Horner said via Reuters.
"We have a safety net but our number one objective is to retain the pairing that we have.
“The next move he [Ricciardo] makes at 28 years of age is a very important one for him. So of course I’m sure he’s going to take the time to make sure the decision is right for him.
“But he knows the intent very clearly, and I’ve discussed it with him, is that we want him in the team. If that takes another six months, then so be it.”
Ricciardo has suffered back-to-back DNFs in Austin and Mexico City, and Horner believes the Aussie will also want assurances over the power unit Red Bull have at their disposal in years to come.
He added: “I think he’s keen to see what engine performance looks like next year, which is understandable."