He is a former shoe salesman who became a household name after being given the reins of AC Milan in 1987. Outspoken and no stranger to unconventional ideas, he argued against the need for man marking or a sweeper, among other things.

His players, including some of the biggest names in the game, were understandably dubious. "Five well organised players can beat ten disorganised ones," he told them. To prove it, he tasked his goalkeeper and a four-man rearguard led by Franco Baresi and Paolo Maldini with keeping their goal intact with just zonal marking. He then told his other players to bombard the defence – but with no specific instructions.

First, he deployed four attackers, then five and six, until there were ten outfield players against a block of four defenders and a keeper. Incredibly the training game ended 0-0. The players, including world-class talents like Ruud Gullit, Marco van Basten, Frank Rijkaard and Carlo Ancelotti, were convinced. The coach's name was Arrigo Sacchi. Today, as he celebrates his 75th birthday, we look back on the legacy of a coach who helped shape the modern game.

Sacchi's playing career was modest in the extreme and confined to the amateur scene. Even after turning his attention to coaching, he was initially limited to small local clubs, obliging him to also work for his father's shoe business. In the Coppa Italia 1986/87, he made headlines with Parma, who he had just brought up to Serie B, by twice beating AC Milan. The club’s owner Silvio Berlusconi had seen enough and made Sacchi the Rossoneri coach the following season.

"I never realised that in order to be a jockey you had to have been a horse first," Sacchi famously quipped when critics questioned his qualifications for the job. As well as being quick-witted, he was also innovative, as he proved by winning the Scudetto in his first season and the European Cup and Intercontinental Cup in each of the next two seasons.

His ideas were radical for the time, but they would later define his playing style and become part of modern football. These included a move away from man marking to the zonal equivalent. An aggressive and high-pressing game was also important, something honed in training through playing shadow football without a ball, as was the need to block the usual passing channels. His teams were also known for staying compact with narrow gaps between the lines and following a clear game plan in every position.

Sacchi long favoured the 4-4-2 system, with the gap between defenders and forwards not more than 25 metres. This compact space was revolutionary at the time, although today it is standard. In order to be able to play like this, the offside trap was a central element of his game plan. At the time, if an attacker was level with the last defender, he was considered offside.

"Italian teams have always focused on defence, but we defended by attacking and putting opponents under pressure," said Ancelotti. "Sacchi had the recipe for a new type of football. His 4-4-2 was, in my opinion, the only way to play modern football."

Roberto Donadoni, another stalwart of that Milan side, also spoke highly of his former boss: "Sacchi started a revolution in Italian football, both in terms of mindset and tactics. We had our way of playing and deployed it against our opponents, from amateurs in training during the week to Real Madrid at the Bernabeu."

In training, the team often lined out in their basic formation, with Sacchi then indicating where the imaginary ball was. His players would move around the pitch accordingly until their positioning became automatic. He had a similarly unconventional method for practicing forward moves, this time with a ball in play but with no defenders. His side would go through their attacking moves in what was effectively an 11-versus-zero game. And while the technique is popular with many trainers today, at the time it had its detractors.

"He got you to repeat the same things over and over, day after day, especially us defenders," explained Maldini. "But if Baresi, Costacurta, Tassotti and I met up today, we could still play together like we did back then. It becomes engrained. That was one of our recipes for success."

Too often Sacchi's footballing philosophy is reduced to his four-man rearguard and defensive ideas, but above all he wanted the game to be entertaining and was a long way from the old Catenaccio style.

"I send my players out to give people 90 minutes of joy," he said. "I always want to have five men in front of the ball when we have possession. And there must always be a player occupying the left and right wings. But that can be anyone and doesn't always have to be the same person."

It was no great surprise when he was appointed Italy coach in 1991. At the 1994 FIFA World Cup USA™, the Ravenna native led the Squadra Azzurra to the Final, where they lost to Brazil on penalties. "Brazil played better and deserved the win," Sacchi said. "I always wanted to win on merit. That's what matters to me."

Two years later at UEFA EURO 1996, his side needed a win in the final group game against Germany to progress. Despite playing brilliantly in phases, a host of spurned chances, including a missed penalty, resulted in a scoreless draw and the Azzurri bowing out. Who knows, maybe with more time to train his players on his methods, Sacchi could have led Italy to a major title.

But what ensures Sacchi’s enduring football legacy is not the major titles he has won, but his influence on the development of the game and the many coaches who are still shaped by his ideas today.