Sebastian Vettel's failure to deliver on his targets at the Ferrari Formula 1 team was triggered by 'insecurity 'resulting from his 2018 German Grand Prix crash, according to Helmut Marko.
Four-time world champion Vettel had hoped to add more title success at Ferrari after joining the team in 2015, but fell short of that target when Ferrari was capable of challenging Mercedes in 2017 and 2018.
After being usurped by new arrival Charles Leclerc in 2019, the team elected to replace Vettel with Carlos Sainz Jr for 2021, with the German joining the newly rebranded Aston Martin team in place of Red Bull-bound Sergio Perez.
But amid some public struggles during a 2020 season in which he only managed to reach Q3 three times in 17 grands prix, compared to 11 Q3 appearances for Leclerc, some have questioned whether Vettel is past his best as an F1 driver.
Marko believes that the 33-year-old has indeed lost his confidence at Ferrari in recent years, and attributes it to his race-ending mistake at Hockenheim in 2018.
Vettel was at the top of the world championship standings and led from pole in the race until he crashed out in light rain, opening the door for Lewis Hamilton to take a victory and a points lead that he would not relinquish thereafter.
Marko thinks there was a lasting impact from Vettel's error, that carried over as the team moved from having Maurizio Arrivabene as team principal to Mattia Binotto taking over.
"I think it's an insecurity that started in my eyes with the crash at Hockenheim in 2018, while leading," Marko told Autosport in an exclusive interview.
"At that time Arrivabene was still team principal. From then on, the relationship with Ferrari has gone from bad to worse.
"How far he was disadvantaged in terms of material, I can't say, but it has to be said that he made far too many mistakes on his own.
"With this crash, the uncertainty set in, and the driving was then very often not at a Vettel level."
Asked if he believed Vettel could rediscover his peak form at Aston Martin, Marko said: "I hope so, for his sake."
Marko and Vettel created a strong bond at Red Bull, with the German taking all four of his world titles for the Milton Keynes-based team.
Vettel had been linked early last year with a potential return to Red Bull amid uncertainty over his F1 future, but the team was clear that it never considered him at the time he was available because it was committed to Alex Albon at that point.