The German would have only been 32 at the start of 2019 but it was a season of change for him and his new team-mate reminded him of his former self.
For the 2019 season, Kimi Raikkonen was replaced by the 21-year-old Charles Leclerc. In a sign of things to come, attention began to turn away from the four-time World Champion and towards a driver very much seen as the future of Ferrari.
Vettel's results also took a turn. Having finished fifth just once in the last 10 seasons, he did so again in 2019 behind his team-mate Leclerc but unlike the last time he finished that low, he had not just won four consecutive titles.
With Leclerc performing well on the other side of the garage, the 32-year-old began to have doubts about his future in the sport.
"[Leclerc was] unburdened by disappointments," Vettel told Der Spiegel when asked why Leclerc was able to beat him in his first year with the team. "Leclerc took the wheel and stepped on the gas. He was lugging less weight around.
"He drove the way I saw myself in my first Formula 1 years."
Ferrari also slipped further behind Mercedes and, had Red Bull not had difficulty in filling their second seat, it is likely his former team would have also finished ahead of them in the Constructors' Championship.
"That did something to me that I didn't directly understand in that way," Vettel said. "Spending so much energy two years in a row, also mentally, and then coming up empty, that's when doubts arose: Is this still going to work?"
Vettel would go on to have his worst season ever in 2020, finishing P13 on just 33 points it what would prove to be his final year with Ferrari.
He moved to the newly rebranded Aston Martin team where he finished P12 in 2021 and is currently occupying 11th this season.
The move did however represent a step down for the German and an acceptance of a midfield battle more than a title fight even if Racing Point had earned P4 in the previous year's championship.
For Vettel, it was a personal matter, to answer questions he felt still lingered.
"Somehow I still had some unanswered questions or unfinished business with myself," he explained. "Can I still do it? Am I good enough to drive at the front in Formula 1?"
"No [the move was not a mistake]. To get answers to the open questions, this time was important.
"The fact that I'm not currently in a race car with which I can show what I'm actually capable of has, however, also contributed to my retirement."
Vettel has just two races left in his F1 career, starting this weekend in Brazil.