Lotus reckons Romain Grosjean now among top four Formula 1 drivers

Grosjean was again Red Bull's main threat for victory last weekend and his second place behind Sebastian Vettel was his fourth podium finish in five races.

The speed that Grosjean has shown over the second half of the campaign has left Boullier in no doubts that Lotus now has a true superstar on its hands.

"We've always known Romain is super fast, actually maybe too fast, and sometimes too fast for his car," said Boullier, referring to some of the wild incidents Grosjean had earlier in his F1 career.

"Having some completeness with his family [he became a father earlier this year] has helped him reach another level of confidence, and then you see the results on track.

"He is starting to be a damned good driver. I think you can rate him in the top three or four today.

"He started to perform well from Germany onwards. There was still a bit finetuning needed on his side, but he has had a very fine second half of the season.

"Now he will start next year in a different mood, and we will have a different perspective from him."

Boullier also thinks that Grosjean has been helped by Kimi Raikkonen's departure from Lotus as it has meant that he has needed to step up to become team leader.

"It is a combination between him [Raikkonen] leaving and his personal life being settled, which brought him a lot of confidence," he added.

"That was maybe the kick he needed to take off."