The signs are growing stronger that 2020 may turn out to be Kimi Raikkonen's eighteenth and final season in Formula 1.

The 2007 world champion is now regularly among the very slowest drivers in the field, as Ferrari-powered Alfa Romeo openly struggles with its 2020 car.

And Raikkonen's long-time racing driver friend Toni Vilander, who is linked with Ferrari through GT racing, is suddenly admitting that the 40-year-old's motivation is finally fading.

"He has said several times that he wouldn't be in F1 unless it was something very important to him," Vilander told the Finnish broadcaster C More.

"But now he is in a difficult situation. Running around at the back, fighting with Latifi and Russell - it doesn't motivate Kimi very much. That's the difficult thing here," he explained.

"If he drove for points and he could battle in qualifying, then Kimi would still be very motivated and do his best to keep going for another season. But now things must be assessed from a slightly different perspective," said Vilander.

However, Vilander admits that Raikkonen is unlikely to be musing about his future too openly in public.

"Kimi is a strange bird of Formula 1," he said. "Usually, drivers of Kimi's status wonder about the right solution and what others think of it. Kimi doesn't think like that at all.

"He makes his own decision. The first person he consults is probably (wife) Minttu."

What Vilander is sure about is that Raikkonen won't quit mid-season.

"No, Kimi wouldn't do that," he said. "He is a professional and will drive what has been agreed. It's not part of the Finnish character to throw the towel into the ring," Vilander is also quoted by Ilta Sanomat newspaper.

"But I know that Kimi is horribly frustrated, and that's the problem. It's hard for him to dig up the motivation if there is not even a glimpse of light at the end of the tunnel."