Valtteri Bottas may be lacking the "hunger" to beat Lewis Hamilton at Mercedes.
That is the view of Mark Webber, who told Britain's Channel 4 that 2019 was "a tough season" for the Finn.
Bottas has kicked off the winter season by winning an asphalt rally at Paul Ricard. He is not ruling out a future career in the discipline.
"You never know. Right now I enjoy it and it's good for my driving skills, but I definitely see myself in Formula 1 for a while," he said.
"I still have a lot to give and many goals to achieve."
Bottas, 30, finished runner-up to teammate Hamilton in 2019, but despite his new beard and early strength, he was ultimately 87 points behind in the end.
"Lewis put the masterclass on everyone," Webber said.
"In terms of wheel to wheel, that hunger, that fight, going down swinging, often we still miss a bit of that with Valtteri," the former Red Bull driver added.
But another former driver, Paul di Resta, thinks Bottas still has a chance.
"He's not as consistent as Lewis, but he was a new person this year," he said.
"You can tell from the way he fought in the first laps that he was more aggressive, so if he manages to take another step, I think he can beat Lewis."
