Cape Town - Pirelli's Mario Isola believes Robert Kubica could have showed his true pace if he was given "more time to adapt" to the tyres.

Reports have been circulating in recent weeks that, finances aside, Sergey Sirotkin also made more of an impression on Williams at the Abu Dhabi test because he was able to extract more pace from the slower tyres than Robert Kubica, who was long considered to be the strong favourite to land the 2018 seat.

But, after speaking to Kubica, Isola has no doubt that Kubica has a good understanding of the tyres and just needs more track time to be able to showcase his true performance.

"I believe that Robert is a professional driver with a lot of experience, even if he didn't drive a Formula 1 car for a long time," Isola told RACER.

"But he has the feeling. Obviously I was asking him for some opinions on the tyres and he has a precise idea on the performance, degradation, how to drive and so on."

Isola then went on to suggest that Kubica's lengthy absence has not been fully taken into account and Sirotkin was always going to have an edge on him after getting FP1 experience with Renault in 2017.

He added: "It is clear that if you take a driver who didn't drive a Formula 1 car for six or seven years and the Formula 1 car he is driving is completely different to the one he left when he stopped.

"Because of the downforce, because of the tyres, because of everything - he actually drove our tyres in the beginning of 2011 in the pre-season test in Valencia, so it's not completely true that he never drove our tyres - he was able to adapt quickly.

"But you cannot pretend that any driver (in that situation) jumping in a car will be quicker than a driver who was involved in many tests or many races.

"Give him the time to adapt and to show us the full potential. I believe he is still a very quick driver."