Red Bull's chief Christian Horner has confirmed that Toro Rosso will not sign Estaban Ocon, due to the driver's connections with rival team Mercedes.

Ocon, 21, made his Formula 1 debut at the 2016 Belgian Grand Prix for Manor Racing and is a product, and still a member of, the Mercedes-Benz driver development programme.

The Frenchman now drives for Force India, but after Williams driver Lance Stroll's father bought out the team, it is looking increasingly likely that Ocon will lose his seat to the Canadian.

“For what is relatively little investment by Mercedes it’s been to their merit that they’ve helped these guys to get into F1,” Horner told Motorsport. “But now it seems to be almost an anchor being a Mercedes driver.

“The crazy situation is you’ve got a driver like Ocon who might end up without a seat next year. If he was to be contractually free he’d be an obvious candidate for Toro Rosso.

"But Red Bull aren’t going to invest in a Mercedes driver, understandably. And I wouldn’t expect the same to happen the other way round.”

Red Bull have had a largely successful junior driver's programme of their own over the years. Sebastian Vettel came through the ranks and went on to win the World Championship four times there.

Meanwhile, the likes of Max Verstappen, Daniel Ricciardo and Pierre Gasly have all benefitted from the programme, with Gasly set to replace the Renault-bound Ricciardo next season.

“It’s very easy to go with something known," said Horner. "And there’s far more perceived risk in taking an unknown quantity or a junior, and I think we’ve demonstrated on numerous occasions that it pays off."

But it represents another dagger to the heart for Ocon, who is rapidly running out of options ahead of 2019.

With both of McLaren's drivers for next year now also confirmed, Sauber or Williams now represent his best opportunity to stay in F1.