Louis van Gaal is an extrovert character. At the beginning of his tenure at Bayern Munich his openness and honesty came across as a little scary for the players. He liked to provoke and challenge them.

He once infamously pulled down his trousers in a team talk to make a point – I was not there at the time, thank God – and the players were surprised and a little shocked. They weren’t quite sure what was going on. He can be like a volcano, very emotional and loud, because he wants the team to succeed. He is a workaholic, who is always going full throttle. And he can be very aggressive with the media, when he considers criticism is not constructive.

There are many stories about him polarising opinion inside and outside the dressing room, and there is a view that he was a staunch disciplinarian, merciless in his decisions. But that is only part of the truth. He is a highly intelligent man who understood that some players are more individualistic and needed different treatment. He did not expect everybody to behave the same way but he demanded respect for the basic ground rules, for the framework of collective work. If you did not get in line, you had a problem.

His demands are high but every manager who takes over from him will find a very disciplined, team-minded group of players – a dream. It is simply great that there’s no one arriving three minutes late for a departure and that you do not have to go looking for players when there is a team meeting. He fosters a spirit of mutual trust.

In terms of tactics Van Gaal is not fixated on one particular formation. He develops the system in relation to the players at his disposal. When he came to Bayern, he identified Franck Ribéry as his key player. He played him as No10 at the tip of a midfield diamond, then realised it did not work. We changed to a 4-3-3 and Arjen Robben was brought in for the right-hand side. But much more important and totally necessary at the time was his introduction of some basic structures and order. We had no left-footed players in the team. Van Gaal promoted Holger Badstuber because he wanted a left-footer on that side of the defence. It doesn’t sound like a big deal but these changes had a huge positive impact in terms of balance and stability.

It took some time for the team to settle and for the results to become consistent but I defended him in front of a doubtful board as I was totally convinced by him. I had never seen such a high level of coaching, it was totally different from what I had experienced as an active professional. In those days coaches moved you around. They had you training in shots, dead-ball situations and stamina. But I had never seen someone who came equipped with a whole, meticulously thought-out concept for practice sessions.

His work with the team was very impressive. There were two basic elements: firstly the individual work with the players – on a technical, tactical and physical level; secondly the physical conditioning of the whole team. All sessions were done with the ball. Van Gaal had players playing four against four with incredible intensity – much more fun than running through the woods. He drilled a passing and possession game into them and they developed a kind of passion for performing. There was an incredibly competitive spirit on the training ground.

Two or three days before a game he would have the “A” team play against the “B” team. The latter played as had to fill in for the opposition. It was a bit difficult at the beginning for the guys in the “B” team because they had to play roles that were sometimes alien to them. He had to coach them a lot, talk a lot, to ensure the exercise was done at a proper level. The match preparation focused on four elements: possession, opposition possession, transition to defence and transition to attack. He gave the players very clear instructions of the sort that you can use on the pitch.

Everybody knew what was expected of them. He improved everyone individually. Bastian Schweinsteiger, for example, became a world-class central midfielder under his tutelage. Collectively the team went up another notch in the space of six months. He gave Bayern a strong football identity that subsequent coaches – Jupp Heynckes, Pep Guardiola – have successfully built upon.

Some of his sessions looked quite banal but each one was performed with maximum intensity. One saw it was obvious that we would have success with him. He won the double and we nearly won the Champions League as well in his first season. The development was there for all to see.

Things took a turn for the worse in the off-season, however. There were clashes with the board and he proved very stubborn. The club wanted to strengthen but he insisted on keeping the squad lean and bringing through young players, like David Alaba. His rationale was to give everyone a realistic opportunity to play; too many unhappy players would have a negative effect on team spirit, he argued.

But a club like Bayern always has to add quality. He underestimated the need for depth in the squad and we paid a heavy price when a number of key players were injured. I was in the crossfire between him and the board but I continued to argue his corner – until he suddenly promoted the inexperienced keeper Thomas Kraft to the starting XI after the winter break, at a time when there was already a lot of disquiet in the team.

At Bayern reaching targets is more important than developing a young keeper. His decision added to what was already a fraught relationship with the board. It was obvious to me that it was only a question of time before everything fell apart. He was fired in April 2011, when qualification to the Champions League was in danger.

The dismissal hurt him. I am interested to see whether he will make Manchester United a possession side. Passing the ball and having lots of ball circulation is sometimes seen as negative when nothing happens but, if that system is played perfectly, it is a very dominant, forceful style and a nightmare for every opposition.

He will shape the squad according to his ideas but he is not dogmatic. United have to present themselves very differently. They have to rebuild and restructure. Van Gaal, with his experience and great touch for youth development, is the perfect man for the job.

I am certain that they will improve. And one thing is for sure: it will not be boring.