Motor racing legend Jackie Stewart is backing Rubens Barrichello to topple world champion Michael Schumacher this year - if Ferrari give him the chance.

Ferrari's claim that their new car will show the biggest ever improvement in performance has sent shock waves through Formula One.

Schumacher deepened the fears by setting a lap record at the team's Fioano test track on his first run in the F2003-GA.

The sport's rulers are desperate to put on a genuine contest after another season dominated by Ferrari and Schumacher. But unless McLaren Mercedes or Williams BMW make a quantum leap, a fifth consecutive constructors' championship looks almost certain for the Italian team. Just as inevitable, it seems, would be a fourth title in a row for Schumacher.

Yet Stewart is convinced Barrichello has the ability and now the experience to oust his team-mate and become the saviour of F1. Stewart, Barrichello's team boss for three seasons before the Brazilian joined Ferrari in 2000, said: "I thought Rubens drove tremendously last season - as well as, if not better than, Michael. And I sense he has acquired the mental toughness any driver needs to succeed at this level.

"The problem, of course, is that while Michael is there he is the No.1. It is very much down to Ferrari."

The Italian team are already under pressure to give Barrichello a fair shot at the title. The FIA warn they will not tolerate a repeat of the phony finish in Austria last year, when Barrichello handed victory to Schumacher.

Ferrari bosses say they won't do it again, though they stand by their right to do "what is best for the team." But they insist they will back whoever emerges as their main hope for the title.

Ross Brawn, Ferrari's British technical director and master tactician, said: "If Rubens gets into the position of having a better chance of winning the title than Michael, we would support him. It is not about favouritism, it's about winning."

That message was echoed by Ferrari president Luca di Montezemolo as he declared: "Our No.1 driver is the one who is the quicker."

It will take more than words to convince the sceptics and if Ferrari are out on their own, the clamour for them to allow their drivers to race will intensify.

Stewart (below) will watch with interest when Barrichello lines up against Schumacher for the start of the season in Melbourne three weeks today.

The Scot said: "I know Rubens well. He is a good man as well as a very talented racing driver. I know you will get the best out of him if he feels he is getting the support and opportunity he needs.

"Of course, Michael has to start favourite and it would be very difficult for Rubens or anyone else to buck the trend, but you never know. Stranger things have happened."

Barrichello, who was privately fuming over the team orders in Austria, is determined to be quickest out of the blocks this year. In his three years with the team he has finished fourth, third and second. Now he says: "I want to win the championship and I believe I can.

"Michael is a fantastic driver, but I have learnt a lot and I am confident my time will come."

Ferrari will follow the strategy that served them so well last year and begin the campaign with the "old" car. Development and test work on the 2003 model will continue until they are satisfied it is ready for its debut.

That could be the third or even the fourth Grand Prix. By then Barrichello hopes to have established himself as Ferrari's main man.