Horner had thought Ricciardo extension 'was a done deal'

Red Bull boss Christian Horner has described how he thought an extension for Daniel Ricciardo had been agreed, before the shock news emerged of the driver's defection to Renault.

"It certainly was initially a big surprise," Horner told Sky Sports F1 on Friday at Spa-Francorchamps. "Obviously the way the momentum had been going, we'd been talking since February about this.

"Dietrich [Mateschitz, Red Bull owner] got involved round Barcelona. By the time we got to the Austrian Grand Prix, the whole lot looked pretty much there.

"There was an agreement in principal. It was about sorting out the papaerwork. Over Hockenheim and Hungary that happened.

"Daniel then decided after Hungary that he wanted a one-year deal. Dietrich agreed to that, and so by Monday afternoon he [Daniel] got the piece of paper he wanted sitting in front of him.

"He drove the car on Tuesday in the test in Hungary, and then I think the flight to America on holiday he decided actually he wanted, despite having everything that he'd asked for, that it still didn't feel right and that he wanted to do something else.

"You have to respect that decision," he said. "I thought he was winding me up to begin with. I thought it was a joke for the summer holiday. I was expecting the paperwork to be signed. He'd even recorded a message announcing his renewal.

• Verstappen doubts Ricciardo has made the right decision

"But the third time he told me I realised it for was real. You just have to wish him well. He's been a great, great driver for us in our team and we'll be disappointed to see him leave."

Horner said that the team had been able to absorb the news over the summer break.

"I think they were pretty surprised. Obviously the announcement came out the Friday just before the summer break. The team have had two weeks of down time to think about it, digest it.

"Daniel was in the factory this week and spoke to his engineers and his mechanics. He spoke to the rest of the team when he got here on Thursday. People are disappointed in one respect but it's Formula 1

"We've got a great pool of talent. We'll be sad to see him go, but equally it opens the door for another opportunity for young Pierre Gasly."

Horner said that the team had always had a back-up plan in mind in case Ricciardo decided not to stay with the team.

"We'd actually discussed it internally before," he said. "The situation was Daniel was dragging and dragging and dragging. At that point it feels like - when both parties want to do something it tends to happen very quickly. This was taking its time so we had to discuss the what-if situation.

"I think Pierre Gasly - another product of the junior team - he's done such a strong job in the Toro Rosso this year. We know him well from his test and reserve times with us at Red Bull, the time that he's had in the car. For us it was fairly clear cut."

However, Horner admitted that it did leave Red Bull with a gap when it came to prospective drivers to take over for Gasly in the junior Toro Rosso squad.

"We obviously have a bit of a gap in the programme," he conceded. "We don't have a driver in Formula 2 or at that level just ready to step in.

"Obviously Toro Rosso will be heavily involved in that decision, but there's nothing obvious. There's a bit of time to take a breath and see what the options are."

The team might be ruing having released Carlos Sainz, who next year will take up a full time race seat at McLaren.

"We chose not to take up that option," he said. "And once Renault had made it clear that they weren't going to go that route either - in Hungary they were progressing with [Esteban] Ocon - we didn't want to hold Carlos back.

"He got an opportunity on the table from McLaren, so we decided to release him from his obligations with us to be able to take up that opportunity."

One suggestion has been a recall for former Toro Rosso driver Jean-Eric Vergne, who has just won the Formula E title.

"He's done a great job in Formula E this year," acknowledged Horner, not willing to discuss the possibility any further.

"I think there's an awful lof of speculation at the moment. The whole driver market has had a bit of a ruffle up and it will be interesting to see what falls out of it."

In the more immediate future, Ricciardo had a problematic first practice session back in the car on Friday, missing all but the final minutes with an engine issue.

"I'm not entirely sure until we get to all the basis of it, but it looks like a fuel injection issue. We'll get a more detail after this session," said Horner.

"Together with the Renault guys we hope to be able to tidy that up in time for the next session."

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