Robert Kubica's return would be a blow to young drivers - Sebastian Vettel

Sebastian Vettel believes Robert Kubica's return to Formula 1 would be a blow to young drivers who are pushing hard to work their way up the motorsport ladder to secure a very limited number of seats, or sometimes no seat at all given how rarely a chance at F1 comes up.

Kubica is pushing for a full-time comeback with Williams this season following his 2011 rally crash, which caused life-threatening injuries and almost saw him lose his right-arm, which still has some mobility issues, though he insists they aren't a barrier to his return.

Vettel though has questioned why Kubica, who turns 33 this week, left it so long to seek a comeback, and although he recognises how it would be "nice story" for Kubica and the sport, he says it comes at the cost of promoting a younger driver to the seat, like Sergey Sirotkin who is also in the running to partner Lance Stroll at Williams.

"I think it's very tragic what happened to him back then, he was considered a future champion," Vettel told Swiss newspaper Blick.

"However, I do not understand why he is now pushing for a comeback. Why did he not do this earlier?

"For him it would certainly be a nice story, [but] on the other hand, it would be a pity for younger drivers, from whom he would take away a race seat."

If Kubica secures the Williams seat, it will mean just one new driver joining the grid in 2018, with Sauber confirming Charles Leclerc as part of its Alfa Romeo deal.