By Andrew Benson Motorsport editor

Button is a very good F1 driver - but just how good?

Jenson Button responds with admirable restraint when the subject of his failure to win a Formula One race is brought up - but then he has had plenty of practice.

The 26-year-old Englishman has started 102 Grands Prix without standing on the top step of a podium - a figure second only to new Honda team-mate Rubens Barrichello among those drivers who went on to win a race.

The 2006 season, which starts in Bahrain on Sunday, provides Button with probably his best chance yet to break his duck, if pre-season testing has provided a reliable guide.

But is Button an all-time great in waiting - or just a very good racing driver who could only win the title if he had the right car?

On the face of it, Button's lack of success has not been his fault - he has never had the absolute fastest car in a race, and only in 2004 was his BAR capable of competing at the front.

Intrinsically, Jenson's driving ability is outstanding John Watson Former Grand Prix driver

Barrichello suffered a similar fate early in his career. The Brazilian spent five seasons with Jordan and three with Stewart without success, but after moving to Ferrari in 2000, he won his 11th race for the team - the 124th Grand Prix of his career.

But the difference between the great and the merely very good is whether they can win when they do not have the best car - as Fernando Alonso did on his way to the title last year.

So far, Button has not shown that ability.

Former Grand Prix driver John Watson, winner of five races in the 1970s and early '80s, says: "I think there were at least two occasions in 2004 where between BAR and Jenson they could have won - at Imola and Monza."

Race report: Imola 2004 Race report: Monza 2004

Watson believes Button has suffered because neither he nor his team have won a race and so do not know what is required.

But, he says, neither does Button push himself or his team as far as, say, Michael Schumacher does.

"I'm convinced if Michael had been in the BAR, they would have won races by now," Watson says.

Former driver Eddie Irvine says there are doubts about Button's absolute ability because he was thrashed by team-mate Giancarlo Fisichella when he was driving for what is now the Renault team in 2001.

Renault's engineering director, Pat Symonds, thinks this is an unfair comparison - but only up to a point.

This year's Honda looks set to give Button his best chance yet of a win

"It was the wrong place and the wrong time," Symonds says.

"The wrong time in that Jenson was the new hero and it perhaps went to his head a little bit, and the wrong place because various people within our team didn't find that at all acceptable. The two combined was a bit of a disaster, to be honest."

But while Symonds believes Button will win a race this season, he has no doubts that team boss Flavio Briatore was right to drop Button in favour of Alonso at the end of 2002.

"There are divisions within the drivers and I do think Michael, Fernando and Kimi [Raikkonen] are in a division of their own, and in that division I wouldn't really like to rank them.

He is good, but he has yet to do anything that makes him stand out from other drivers From U1636318 Have your say on the Five Live messageboards

"Then you have this big division two, which has all sorts of people in it, your Giancarlos, your Barrichellos, your Montoyas, and of course Jenson.

"It's as difficult to put a ranking on those. Jenson is certainly at the top of it, and a lot of his races have been pretty damn good and you know he can do it. So he's outside the top three, but probably inside the top six."

John Watson believes Button's natural talent is of the highest level - but that he lets himself down in other areas.

Button enjoys the glamorous lifestyle F1 affords him

"Intrinsically, his driving ability is outstanding," Watson says. "The thing that seems to be not coming together is that intangible quality that certain people have - Jackie Stewart, Niki Lauda, Ayrton Senna, Alain Prost, Schumacher - to take a team and make it what you want.

"The key is the driver role. He can give so much to the team. It's about a level of commitment, and it makes people believe in you to such an extent that they will go through hell and high water for you."

Button's ability to achieve that was undermined by the farce over his future that rumbled through 2004 and '05.

Button hits back over criticism

His failed attempt to move to Williams while contracted to BAR in 2004, followed by buying himself out of a commitment to join Williams for 2006 to stay at BAR, was a "debacle that diminished Jenson's standing within the industry", Watson says.

And Watson compares the low-profile lives led by Schumacher and Alonso outside F1 with Button's regular appearances in the gossip pages of tabloid newspapers.

"Jenson enjoys being a racing driver and the trappings of it. That's fine. But he has to rationalise that aspect and put it into context."

It is no exaggeration to say that 2006 could make Button - or ruin him.

With Barrichello arriving at Honda as his team-mate, Button has in the same car as him a man who not only is a known quantity, but who is very fast, highly rated and hugely experienced.

Barrichello's arrival could make life very difficult for Button

Barrichello comes to Honda after six seasons at Ferrari, where he established himself as Schumacher's fastest ever team-mate.

He was rarely a match for the German, but there were weekends when he had the beating of him.

Barrichello also brings with him the education of seeing how Schumacher moulded Ferrari to his will.

Not only that, but Button has been at BAR-Honda for three seasons, so should have the team fully around him, and to have gone at least some way to making the car suit him rather than Barrichello.

The implication is clear - if Button cannot beat Barrichello in what is effectively his own team, then he will never again be regarded in F1 as a man who can lead a team to championship success.

But the opposite is also true - and the fact that Button subdued the headstrong and political Jacques Villeneuve when the Canadian was his team-mate in 2003 suggests he has at least the mental strength to handle Barrichello.

As Watson points out: "Should Jenson win a race, and should that lead to him winning lots of races, all this will be redundant."

But as long as he does not these questions are still hanging over him.