Jackie Stewart has warned Lewis Hamilton that he should not automatically expect to be a title contender in this year's Formula One world championship.

McLaren driver Hamilton, 23, only missed out on becoming the first rookie world champion in the sport's history by a point last year, but the pre-season testing form of his team has given the Brit big hopes for the season ahead.

Stewart though, who won the world title in 1969, 71 and 73, said that he would not be surprised if the rookie sensation was less impressive in his second year.

"It's not unusual for a new driver like Lewis to struggle a bit in the second season," Stewart told The Herald newspaper.

"He is no longer an unknown quantity; he is in the position where people are expecting him to win every race he starts, and although I have no doubt he will be competitive, I wonder whether he will have the car to take on Ferrari in 2008.

"It's a curious thing - Lewis will think he can nail this year's championship, because he came so close last time around, but that can make you push too hard and, before you know it, little things can start going wrong which make the difference."

Stewart believes that McLaren newcomer Heikki Kovalainen could use his status as a still somewhat unknown quantity to surprise Hamilton in the same way that the Brit did to two-time world champion Fernando Alonso last year.

"Suddenly, here is another bright-eyed, bushy-tailed contender," Stewart added. "If Heikki makes a good start in the first few races, the publicity and press attention might revolve round him."

And he also pointed towards McLaren's tumultuous 2007 season, which included the spygate scandal, a fall-out between Hamilton and Alonso, and the racist abuse suffered by Hamilton at a recent Barcelona test, as having disrupted the team enough to allow Ferrari to steal a march on them over the winter.

"I know McLaren will insist it is business as usual, but they have had to deal with all kinds of external issues, including the racist abuse which Lewis faced in Barcelona and, no matter how professional you aim to be, these matters all deflect a team from their prime concern, which is putting together the best car," he added.

"McLaren, at the moment, are under scrutiny in everything they do and everywhere they go, so they really need to keep their heads down and concentrate exclusively on racing affairs in the months ahead if they are to improve on 2007, when all [their] difficulties caught up with them in the last two grands prix and they allowed the opportunity to slip away. I wouldn't write them off, but it might be hard to build up that momentum again.

"None of this changes my opinion that Lewis Hamilton is an extremely talented young man, who has the ability and the attributes to win the F1 title, but a lot of factors have changed this season and Kovalainen's arrival at McLaren could mean that the shoe is on the other foot."

Jamie O'Leary / Eurosport