HOW can we evaluate the career of Michael Schumacher? Statistically, at least, he is the greatest driver in history.

He has raised the bar in terms of what is expected of a grand-prix driver; commitment, fitness and preparation are the hallmarks of his work. As a child racing karts, he developed the view that you get out of racing what you put in. Rarely has any sport seen a harder worker.

At Ferrari he built around him a team of engineers and managers, ruled by a “circle of fear”, in which the key players were motivated as much by a desire not to let the others down as by the thirst for victory. After 21 years without a world title, Schumacher gave Ferrari five in succession from 2000 to 2004.

As a pure driving talent, he is up there among the greats, but, as he admits privately, he has rarely had a driver of his own level to race against. His battle with Ayrton Senna was in its infancy when the Brazilian was killed in 1994.

Mika Hakkinen challenged and beat him in the late 1990s, but he lacked Schumacher’s strength and consistency. Only in the past two seasons, with the rise of Fernando Alonso, has Schumacher come up against a driver truly on his own level. They have raced hard this season and honours have been evenly split between them, but Alonso has had the upper hand. With the arrival of Kimi Raïkkönen at Ferrari, Schumacher has chosen this moment to make his exit rather than face the ignominy of being thumped by the younger men.

It is the first time that Schumacher has ducked a challenge. Few drivers in his position as world champion in 1995 would have taken on the task of rebuilding a moribund Ferrari team.

The years while Schumacher was toiling to get the team in shape allowed Damon Hill and Jacques Villeneuve to win their championships. It could have been Schumacher in their cars, and it would have been had his thirst for a challenge not outweighed his desire to win at all costs.

But if he is to be lauded for his sporting spirit in reviving a faded brand, there is also a darker side to Schumacher’s genius. His willingness to punch below the belt was forged early in his career.

When he deliberately drove Hill off the road in Adelaide to clinch the 1994 drivers’ world title, many wondered why he felt he needed to do such things as clearly he was a vastly superior driver.

Schumacher came of age as a driver when the sport was ruled by hard men such as Senna and Alain Prost, who had a history of committing professional fouls on each other. He thought that this was how things were done. He got away with it in 1994, but when he tried it again on Jacques Villeneuve at Jerez in 1997, the world had moved on. He remains the only driver to be disqualified from a championship for unsportsmanlike behaviour.

This year he was found guilty by the race stewards in Monaco of deliberately parking his car on the racing line during qualifying, to stop Alonso from beating him to pole position. It seemed an odd moment for him to remind everyone of the bad things that he has done.

Such is the enigma of Michael Schumacher; an exceptional driver who has given the sport so many great moments, but also some darker ones. Will history revere his prowess or judge him harshly for his weaknesses? I think the former.

• James Allen is the Formula One commentator for ITV Sport and the author of Schumacher: Driven to Extremes, published by Bantam.