Jacques Villeneuve believes that Sebastian Vettel needs to mature psychologically in order to make the most of his talent.
The 2010 World Champion was highly criticized for what were perceived as petulant reactions to his shunt with team-mate Mark Webber in Turkey and the drive through penalty imposed on him by stewards in Hungary.
Villeneuve is of the opinion that Vettel needs to quash such tendencies if he is to retain his World title.
"He will still be fast, of that there is no doubt," Villeneuve told T-Online.de.
"The question has always been his psychological maturity. And viewed from the outside, it is impossible to say how this has developed. This will show the first race."
In what will perhaps be a surprise to some, Villeneuve has defended arch rival Michael Schumacher after the German's largely unimpressive return to the sport.
"The first of the season was tough, but in the second he was really strong," explained the 39-year-old.
"He was criticised because he didn't simply blow Nico [Rosberg] away but if you look back at his time at Ferrari he was never more than 0.1 to 0.3 second faster than his team-mates, so why should he be seconds faster than Nico?" questioned the Canadian.
