Lotus Renault GP boss Eric Boullier has admitted that Robert Kubica is unlikely to race again this season.

As the popular Pole recovers from the numerous injuries sustained during a rally in early February, Boullier admits that it is almost impossible to say when the highly talented racer will return to the cockpit, though he doesn't rule out an appearance during one of the Friday practice sessions later in the year.

"We will probably manage for him to do a Friday session at some point in the year," he told Spanish radio station Onda Cero, "but for sure his return this season will not be possible.

"Robert has survived an impressive accident," he continued, "and now he has to do the hardest thing, to recover fully, which is something that nobody knows whether he will succeed. Not him, nor the doctors, nor us."

Two weeks ago it was revealed that Kubica is entering the second phase of his recovery process, which involves heavy rehabilitation aimed at restoring functionality. Further operations are planned to remove the adhesions that are affecting the functionality of his forearm and elbow muscles but these are considered routine practice.

Speaking at the end of April, before he was released from hospital, Kubica revealed that he is in regular contact with his engineers and following the team's progress closely in anticipation of his return.