After witnessing Robert Kubica's performance this season, 1997 world champion Jacques Villeneuve says there are no doubts that Robert Kubica is slower than Williams team mate George Russell.

Kubica's miraculous comeback to the pinnacle of motorsport after his 2011 rally crash and seven years of absence, and which was hailed by the F1 community, is slowly but surely turning into an agonizing sporting wreck for the 34-year-old Pole.

Granted that Williams' FW42 is currently not up to standard, but Kubica's performance relative to Russell has been a one-sided affair in favour of the young F1 apprentice.

"I was not a fan of him returning. For me Formula 1 is an elite, it is for the absolute best," said Villeneuve in Montreal.

"The only thing that counts is that Robert is clearly slower than his team-mate, who is after all a rookie. Results matter here.

Earlier this year, Kubica justified his under-performance by claiming that his FW42 had embedded deficiencies compared to Russell's mount.

But in Barcelona, when Williams switched chassis and the Pole was supplied with Russel's car, there was no improvement and the performance delta between the two drivers - whether in qualifying or in race trim - has persisted.

Villeneuve doubted however that there were any significant differences between the Grove-based outfit's cars.

"I do not know, I’m not in the team," admitted the Canadian.

"You cannot see everything from the outside. But such situations in Formula 1 aren't likely to happen. These cars are very similar to each other.

"I don't know… Maybe the settings don’t match Robert’s style, and they suit Russell."

Gallery: The beautiful wives and girlfriends of F1 drivers

Keep up to date with all the F1 news via Facebook and Twitter