Two contemporaries of his father are unsure Nelson Piquet has done enough in his rookie season so far to secure his future on the formula one grid.

The Brazilian newcomer secured his maiden podium at Hockenheim nearly two weeks ago, but Alan Jones, the 1980 world champion, and British driver Derek Warwick, are still not convinced of Piquet's talents at the wheel of the 2008 Renault.

"Compared to the achievements of other drivers such as Raikkonen, Massa, Kubica, Alonso or Hamilton, Piquet has delivered too little," Warwick, who contested more than 160 grands prix in the 80s and 90s, is quoted as saying by Die Welt.

In the 80s, 23-year-old Piquet's father and namesake won three drivers' world championships.

Australian Alan Jones, the title winner in 1980 - 13 points ahead of Piquet Snr - is also unimpressed with Piquet Jr's performances so far alongside Fernando Alonso.

"In Piquet's (Snr) first season in 1979, he had his own teammate Niki Lauda, also a twice world champion then, until control," Jones remarked.

Jones said of Piquet Jr: "He's a good driver, but the strength, the determination, the aggression, not to mention the outstanding talent of his father, seem to me to be missing."

Piquet, always with his father's status, support and money behind him in his formative racing days, has endured his fair share of criticism as he struggled in the R28 in 2008.

But Pat Symonds, Renault's engineering chief, thinks the Hockenheim podium might have been a turning point.

"Very often when a driver has had a difficult start to their career, they get a good result and after that nothing seems to stop them," he said.

Symonds continued: "It's fair to say that he has found the pressure quite difficult this year, but the result in Hockenheim is the perfect response from him."

Source: GMM