Christian Horner says Sebastian Vettel may switch to Mercedes in 2018

Sebastian Vettel (left) examines the car of Lewis Hamilton after Hamilton qualified on pole for the Canadian GP on June 11, 2016, at the Circuit Gilles Villeneuve in Montreal, Canada.

Sebastian Vettel’s former boss thinks the German driver may soon run out of patience for Ferrari.

Christian Horner, who oversaw Vettel’s four consecutive world championships for Red Bull, told Sport Bild that he senses a lack of calm in the 29-year-old’s current disposition.

"I have the feeling that Seb is a bit rattled," Red Bull team boss Horner told the German newspaper.

"I know from personal experience that he has to feel good in order to perform well. And I’m not sure whether he likes (Ferrari president) Sergio Marchionne’s pressure.

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"I can well imagine that in 2018 Seb will switch to Mercedes if he doesn’t start making progress with Ferrari," Horner added.

The Italian press is currently characterizing Ferrari as being in "crisis," having failed to capitalize on its progress and being out-performed in recent races by Red Bull.

But Gerhard Berger does not agree with Horner that Vettel is becoming rattled by the pressure.

"I know him from the Red Bull days," the former Toro Rosso co-owner told Italian newspaper Corriere della Sera, "and he is a true leader. He never loses heart."