Motor Sport Brazilian Grand Prix: Richard Williams surveys the attributes that made Michael Schumacher arguably the best Formula One driver of all time.

No matter how complex the technology of Formula One becomes, in the end the most sophisticated and critical piece of machinery in a racing car is the man at the wheel. Which is why, as Michael Schumacher prepares to take the grid for the 249th and last time tomorrow in Brazil, the search is on for the man who can fill the gap that will be left by the departure of the seven-time world champion.

For if Schumacher's career proves anything, it is that however much the engineers seem to be in control of the sport, with their multiple 24/7 wind tunnel operations and their serried ranks of anonymous software programmers, the driver is the component which makes the difference between winning and losing. And if there are barely a couple of dozen men in the world capable of competitive performances in a contemporary grand prix car, there may be only one in every generation in whom the qualities that make a multiple world champion can be identified.

Were it otherwise, were the drivers as interchangeable as lightbulbs, then such able men as Martin Brundle, Johnny Herbert, Eddie Irvine and Rubens Barrichello - the most prominent of Schumacher's team-mates over the past 15 years - would have enjoyed the same kind of headlines. Instead, the most decorated racing driver of all time will go into retirement tomorrow night knowing that, at 37, he remains the most feared competitor on the grid, the one who set the standards by which his rivals are judged.

And whereas some of them may get close to him in one aspect or another of the Formula One driver's tradecraft, so far none has equalled his mastery of the full range of attributes. Ross Brawn, his technical director during his championship years at Benetton and Ferrari, puts it simply. "Michael understands the big picture," he says.

Schumacher's pure speed, his supremely intelligent approach to race strategy, his mental toughness and his profound rapport with his engineers are among the fundamentals of his success. Even more basic, however, and more difficult to copy, is a degree of inherent enthusiasm - there is no other word for it - that has led him to work harder at the job than any of his rivals, and that tends to have a powerfully motivating effect on the designers, engineers and mechanics with whom he makes common cause.

What the average fan sees is a driver who can put everything into a pole-position lap, who can suddenly, at a crucial period in a race, reel off a dozen laps at a pace that destroys the opposition, and who is willing, when the occasion demands it, to stake everything on a single, high-risk manoeuvre.

In the opinion of the man who has worked with him more closely than anyone, the particular quality that marks him out from the rest is an instinct that allows him to enter corners at the highest possible speed.

"That shows such a high level of commitment," Brawn said, "and a confidence that he can cope with whatever is going to come. Lots of people can come through the middle of a corner and make their exit well, particularly with traction control, where you just put your foot down in the middle of a corner and the system takes care of everything. But on the entry to a fast or medium-speed corner, there's no substitute for driver ability. That's where we see the difference."

Yet behind all those spectacular Sunday-afternoon moments lies a cheerful acceptance of unseen drudgery. Because he has never fallen out of love with the job of driving a racing car, Schumacher tends to train harder and to invest more time in the dreary but essential work of testing than anyone.

He established new benchmarks in these areas long ago, but even after 30 years at the wheel of one machine or another, from his first kart to his last Ferrari, he maintains a rigorous approach that is equalled by no one else on the grid, although he must have grown used to hearing other team bosses urging their young prospects to follow his example.

As a result of that readiness to tackle whatever work needs to be done, three years ago the German surpassed the mark no fan of motor racing expected to see matched: the five titles won by Juan Manuel Fangio half a century ago. On the way, Schumacher easily overtook Alain Prost's record of 51 grand prix victories; now he has almost doubled the target at which his successors must aim. This year, too, he erased Ayrton Senna's pole-position record.

But to believe Schumacher's tally of seven titles, 91 race wins and 68 pole positions will never be eclipsed is to deny the lessons of history. Sooner or later there is always a Tiger Woods to set off in pursuit of Jack Nicklaus' 20 golf majors. The competition may grow fiercer and the standards of technique and fitness may rise, but eventually a competitor emerges with a range of attributes that combine into something we can only describe as genius.

Such a man was Schumacher, who exceeded Fangio's mark by achieving such a level of consistency that the occasional stumble would send waves of astonishment through the paddock.

Only in the dimension of sporting ethics could he be faulted, yet that lurking unscrupulousness, combined with the self-confidence that some believed shaded into arrogance, simply added an extra weapon to his armoury.

Schumacher acquired some of his less attractive on-track habits from Senna before watching the Brazilian disappear from the scene as he himself was rising to prominence. Now he ends his career in a shoot-out with Fernando Alonso, the young pretender who took the title last year and is odds-on favourite to retain it tomorrow.

Among the group of five experienced but still young drivers who can be expected to compete next season for the vacancy at the pinnacle of the Formula One hierarchy, Alonso looks the best equipped. But the young Spaniard's decision to leave Renault for McLaren next season appeared to be conceived in haste and may be repented at leisure.

Harsh as it may seem, the departure of a great champion should kick the cycle of renewal into life.

• Guardian Service