Sebastian Vettel seems to have reconciled with the notion that his Formula 1 career is over.

Although he hasn't completely ruled out a return, the four-time world champion isn't actively pursuing a comeback, according to one insider.

During the recent grand prix weekend at Imola, Vettel showcased his 1993 McLaren and paid homage to Ayrton Senna and Roland Ratzenberger. Following the tribute, he shared with the press: "Of course I've thought about returning and I knew beforehand that I would think about it."

"But in the end nothing has changed."

In late March, Vettel was deeply involved in testing a Porsche hypercar, yet he isn't participating in next month's Le Mans, with Porsche admitting that it prefers drivers with more endurance racing experience.

Christian Danner, a former F1 driver, sensed at Imola that Vettel has also come to terms with his departure from Formula 1 racing.

"Firstly, he probably noticed that he wasn't in great demand," he explained to motorsport-magazin.com. "Secondly, I think he realised what it would mean - the energy you have to put into it and the training you have to do for it."

Danner also suspects that Vettel has ceased all racing-related physical training.

"When I saw him standing there (at Imola) and shook his hand, I thought he looked a bit pale and gaunt," he remarked. "He wasn't bubbly and effervescent like we've seen before. I hope he's well."

Other observers have also noted that Vettel, once a prominent figure at Red Bull, Ferrari, and Aston Martin, seems to have lost the robust, F1-typical physique - particularly the neck.

"He can train a lot," Danner noted, "but I think reality is speaking clearly for Sebastian."

"I hope he will find that sense of wellbeing that is so difficult to regain when you're no longer behind the wheel," he continued. "That great feeling you get when you drive a Formula 1 car."

"I'm keeping my fingers crossed for him, whatever he does - whether it's motorsport or something else."