Is Ferrari's temperamental champion now yesterday's man?

Chatting to Anthony Davidson at Daytona back in 2013, I asked him for his thoughts on the coming Formula 1 season. He didn't hesitate: "Sebastian Vettel will win his fourth world championship - I'd bet my house on it, and why? Because the rules haven't changed, which means you can still have a blown diffuser - Adrian Newey is the master of designing it, and Vettel's the master of driving it.

"If we were talking a year from now, when the rules change hugely, I wouldn't have a clue about the season to come, but for now I think there's no way Vettel and Red Bull will lose..."

Davidson was spot on. Although Sebastian won only four times in the first half of the season, after the summer break he never lost a race, reeling off nine on the trot, a string of faraway grands prix seemingly blurring into one triumphal procession. "We need to remember the good times, boys," he radioed in as he put the Red Bull into a series of victory donuts in India. "It won't always be like this..."

And it wasn't. In 2014, when the hybrid engines arrived and the blown diffuser disappeared, Vettel didn't win a race - and what made it worse was that Daniel Ricciardo, his new team-mate, put three on the board.

Throughout that year Sebastian was in a resolutely bad mood, missing no opportunity to stress his dislike of the new, heavier cars, the hybrid engines that powered them, and the Pirelli tyres on which all were required to run.

Before the season began, Mark Webber, his erstwhile team-mate and sometimes bitter rival, told me he doubted Vettel was in this for the long haul. "He's got his championships early, going to have a kid early, and I think he'll retire early - probably a blast in the red car, then sayonara."

About the red car, anyway, Webber was on the mark. By August Vettel had made arrangements to move to Maranello, for so long the province of his idol, Michael Schumacher.

"I never understood Seb's awful season, when Ricciardo arrived," says Martin Brundle. "He'd just won four championships, for God's sake! He kept on about how he hated the hybrid cars - but when he got to Ferrari he was immediately on the pace, and I've always wondered if he went slowly in 2014 because he needed to trigger his Red Bull exit clause. Whatever, he had to leave, because another year like that with Danny Ricc, and his value would have been nothing..."

Like every new Ferrari driver, Vettel began with the highest of hopes. He won in Malaysia, his second race with the team, but only two more victories followed in 2015, and it wasn't long before he began to understand the frustrations that had driven Fernando Alonso out. Five seasons have produced only 14 wins, assuredly far short of what he expected.

It must be said, however, that there would have been more had Seb not become prone to making mistakes under pressure, a trait far more evident than in his earlier years. Most disastrous of all was understeering off the road at Hockenheim in 2018, when leading his home grand prix, but there have been many others, too.

"I think," says Brundle, "that Vettel's judgement in wheel-to-wheel combat has gone, and that's critical. He's always operated on a pretty highly strung level, but these days his default mood is to get angry, forever moaning about backmarkers, and so on, and that's sad. I remember when he'd turn up with a rucksack, smiling, ready to go - I adored him in those days."

Me, too. I think of Barcelona in 2007, when the BMW press officer said to me, "Come and have breakfast tomorrow with my new schoolboy..." I did, and was charmed. Sebastian, 19 but looking nearer 12, was the team's test driver, and if he was thrilled to be on the verge of a Formula 1 career, so also he delighted in telling me of his love of British comedies like Monty Python and Fawlty Towers. Even more unexpected was his fascination with motorsport history.

This is not your typical 21st century Formula 1 driver. A deeply private man, he keeps his professional and family lives well apart, and - wisely, in my opinion - doesn't want to know about any form of social media.

In recent years, though, Vettel's demeanour at the race track has indeed changed. Although still genial much of the time, quite often he is sullen and unsmiling, disappointed by Ferraris invariably not quite on the pace of Mercedes, and perhaps dismayed by the errors of judgement which have crept into his driving, as at Monza last year, or Silverstone where he clattered into Max Verstappen.

"Seb's Achilles Heel," says David Coulthard, "is that he's still got that 'throwing toys out of the pram' behaviour. He definitely has a problem with that - and Baku in 2017, when he nudged into Hamilton during the Safety Car period, was a case in point.

"Pushed to his raw racing instincts, Vettel is emotional and reactive. You could say that those characteristics are what has made him great, but equally they've been a weakness throughout his career.

"Remember his reaction after the coming-together with Webber in Turkey? He blamed Mark, but it was his fault, and it was the same at the start in Singapore in 2017, when he took out [Kimi] Räikkönen and Verstappen, as well as himself.

"He'll never, ever, admit that he was at fault - in that respect, he's very like Michael..."

Of late, too, there has been pressure from his team-mate. For four years Räikkönen was in the other Ferrari, and that was fine: the two men got along well, and Kimi was no longer quick enough to be other than an occasional threat. Not surprisingly, Vettel fought strenuously to keep him in the team, but in 2019 Charles Leclerc arrived, immediately - expectedly - proving an entirely different proposition. In Bahrain, only his second race, he dominated until engine problems intervened.

Usually Leclerc was the quicker Ferrari driver, although Vettel looked his old self in Montreal, where he took pole and held off Hamilton to the flag, despite a brief off, only to be robbed of victory by a stewards' penalty which most felt unjust. For a time thereafter he seemed thoroughly detuned, although there was a late season resurgence, and he won - perhaps fortuitously - in Singapore.

Now, though, Sebastian faces an uncertain future, for while his Ferrari contract has but one season to run, Leclerc's has recently been renewed - carrying him to the end of 2024 and removing any doubts as to where the team's emphasis now lies.

One hopes that Vettel will rise to the challenge, get himself back to something like the blinding form we saw for so long in his Red Bull days, but that seems unlikely. Beyond question he has been a great driver, albeit not in the 'all time' category for which he once seemed destined, and there will still be occasional days in the sun, but probably - sadly - Brundle is right: "It would be foolish to write Seb off, but I do believe his best is behind him."