Jun.25 (GMM) No fewer than four drivers have outclassed Lewis Hamilton so far in 2008, according to former formula one team chief Gian Carlo Minardi.

The Italian told minardi.it that, notwithstanding the McLaren driver's Melbourne and Monaco wins, he believes four of 23-year-old Hamilton's competitors have been more impressive this season.

"Robert Kubica has committed no errors, with his only tally of zero points in Australia with the collision with Nakajima, that was not his fault.

"Without that, he would be far ahead in the championship," Minardi, who at the end of 2000 sold his Faenza based squad to Paul Stoddart, said.

"Another one, certainly, is Fernando Alonso, who even with an uncompetitive machine always shows something. And, of course, the two Ferrari drivers," he added, referring to championship leader Felipe Massa, and his teammate Kimi Raikkonen.

However, 60-year-old Minardi is reluctant to be too hard on Hamilton, predicting that he will be among the top drivers in the future.

"But at the moment, he is committing very serious errors of inexperience and displays an excess of nervousness.

"Over the next grands prix he must demonstrate his ability to improve in these areas."