After years of setting lap records, Sebastian Vettel fears Formula 1's new 2021 cars could be underwhelming in terms of performance.

On Thursday, Liberty Media revealed the final proposed design seeing a significant shift from the current philosophy with much simpler front and rear wings, no bargeboards and instead bigger venturi tunnels for greater ground effect.

Estimates on how much lap times would increase under the new regulations have been mixed, but now FIA head of single-seater development, Nikolas Tombazis, reveals the new cars should sit between the current generation and those used until 2016.

“We are expecting cars to be approximately 3-3.5 seconds slower per lap,” he said. “But we don’t think that is the key parameter of the spectacle. We feel the raceability is the main target."

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Indeed, even the former Ferrari chief admits that estimate may not be an accurate one.

“We haven’t been focusing on an exact level of performance," he explained.

“We cannot predict exactly where the downforce will end up compared to the current cars, it will be a bit less after the development has been carried out.

“But even the car that has been developed in CFD and developed in the wind tunnel has already got a respectable amount of performance.

“And it has been developed by a relatively small number of aerodynamicists and hours in the wind tunnel compared to a normal team.”

Despite the suggestion that there is a lot of potential to unlock, Vettel isn't convinced by the direction F1 is taking.

"I think the cars are a lot more spectacular since 2017," said the Ferrari driver. "Now we know what the cars can do, it was quite slow before that.

"Obviously we had very little drag and it was great in a straight line but that's not the exciting bit for us and it was significantly slower than maybe some years earlier.

"The wrong direction, in my point of view, is that the cars are so heavy," the four-time champion noted.

"Which is obviously related to, in a way, some of the safety measures, but I think everybody accepts that and the power unit.

"So that is really, I think, the biggest difference if you really make a big [comparison] between now, where we are, and where Formula 1 has been 10 or 20 years ago."

Should Kimi Raikkonen continue in F1 in 2021, it would be the fourth different era of car design he has driven and given that experience, the 2007 world champion claims single-lap pace isn't so important.

“I don’t think three, four, five seconds makes any difference,” he told RaceFans.

“Like if you take qualifying, yes, we are fast, but in the race we are probably five, six seconds with fuel and everything else.

“I think even if we are 10 seconds slower, for people to watch the races, if it’s more exciting nobody cares. Every year the times are slightly different.”

Max Verstappen added: “At the end of the day, it doesn’t really matter how it looks or whatever, as long as it gives us better racing and we can follow better.

“Of course we want to be within two seconds, three seconds of what we are doing now, definitely, because if it’s going to be about four or five it’s not what we want, because then it feels a bit too slow."

When told the expected performance was somewhere around what was seen in 2016, the Dutchman continued: “To be honest I didn’t really enjoy driving the cars as much back then as I do now.

“But of course you have to find a middle way in terms of what you want with following and stuff like that. Anyway, throughout the season the cars will improve.”