Robert Kubica’s return to Formula One after last month’s horror crash is impossible to predict, his Lotus Renault team doctor Riccardo Ceccarelli admitted yesterday.

“When will he return? Now that’s a question to which no one can reply for the moment. All we know is that it will be very long,” Ceccarelli said.

“There are two positive things – the work of the doctors and Robert’s physical and psychological response which is really very strong.

“For us who know him well there is no surprise. Robert doesn’t surprise us by his capacity to react quickly and well. On the other hand, the hospital doctors are astonished,” he said.

Ceccarelli added: “We don’t have a return date to give. We really can’t anticipate what will happen... I won’t talk about neither next year or the following year.

“We’re doing our job from day to day, the best possible and afterwards we’ll see. It will take time.”

Kubica underwent surgery three times after crashing while competing at the Ronde di Andora Rally in Liguria, Italy on February 12 and is still being treated in the same hospital near Genoa.

Lotus Renault have signed German driver Nick Heidfeld to replace Kubica for the upcoming season.