Leeds United boss Marcelo Bielsa is one of the most influential coaches football has ever seen - according to those who have worked with him.
Manchester City boss Pep Guardiola hails the Argentine as his mentor, while Tottenham Hotspur head coach Mauricio Pochettino calls him his football father and former Barcelona manager Tata Martino claims those from the Bielsa mould are his "disciples" - but what have those in the game all said about his influence?
Let's take a look...
Pep Guardiola - Manchester City manager
"My admiration for Marcelo Bielsa is huge because he makes the players much, much better. Still, I didn't meet one guy, a former player from Marcelo Biesla who speaks no good about him. "They are grateful about his influence on their careers in football.
"He helped me a lot with his advice. Whenever I speak with him I always feel like he wants to help me.
"It is important for me to say this about Marcelo because it doesn't matter how many titles he had in his career. We are judged by that – how much success we have, how many titles we have won.
"But that is much less influential than how he has influenced football and his football players. That is why, for me, he is the best coach in the world."
Mauricio Pochettino - Tottenham Hotspur manager
"He is like my football father. We are a generation of coaches who were his disciples. "How he feels football, the passion he has for football, I think we all took that from him."
Diego Simeone - Atletico Madrid manager
"I have the influence of several coaches: Bielsa, Eriksson, Basile, they have all left a mark. Bielsa taught me the most."
Tata Martino - Atlanta United manager (former Barcelona and Argentina head coach)
“Bielsa is the most famous coach. He had a big impact on us as coaches.
“He only coached me for four years but it is enough. We are all disciples of Bielsa.
“He is called Loco because the thinkers in football are usually called Loco. He is definitely not crazy.
“He has charisma, and it’s important, but charisma is not enough. He is also very intellectual. He leaves a mark wherever he has gone.
“He is a coach that players want to play for. He has left a footprint wherever he has been, at Newell’s for sure but also in Bilbao, Chile, Marseille, Argentina.”
Marcelo Gallardo - River Plate manager
“Bielsa was one of the coaches who taught me the most, but maybe I missed some of his concepts because I was very young and they didn’t interest me that much at the time.”
What about others in the game?
Andrea Radrizzani - Leeds United owner
"He is a coach that I have admired for many years and when the opportunity arose to bring him to Elland Road, we made it our top priority for the summer. Marcelo has a wealth of experience and he will use that to create a new culture and a winning mentality at our football club."
Angus Kinnear - Leeds United managing director
"He sees the potential (in Leeds) and is a football romantic. He knows it would be a great way to top off his CV by getting Leeds promoted.
“Andrea and Victor met him for two days and myself and Victor went out for another two days and we effectively had a four day discussion, he not only has a fantastic understanding of our team, but also our league as well.
“In our first meeting with him, he already had technical drawings of Thorp Arch and very clear ideas on the layout and how it needs to work from a functional basis to deliver on his principles and methodology."
Gabriel Heinze - former player
"I don't know if there is a secret to Bielsa and how he does so well. I know one word to describe him - that's work. He works very hard, he displays passion, devotes his life to what he does, but I don't know if there is any secret."
Fernando Llorente - former player
"At first he seems tough and he may even annoy you with his persistence and don't take no for an answer resilience but in the end he is a genius."
Benjamin Mendy - former player
"He made me devour videos like never before. To begin with he put me in front of the videos and I'd fall asleep. But he was happy! I was shocked. After a while I stopped sleeping and told myself go on, I'll watch two minutes of this thing after all.
"After that he talked to me, I talked to him and we'd go over moves together. He told me, see, that's why I let you sleep. You slept, you slept, you slept but the day you decided to watch you got interested on your own. If I'd pushed you to watch you wouldn't have been interested. Marcelo is just too good."
Alexis Sanchez - former player
"I learned a lot from him and it is because of him that I am who I am. What I remember the most about Bielsa was the mentality that he tries his players to have."
Javi Martinez - former player
"There are days when he doesn't leave the training ground until the small hours, it is insane."
“For me what Bielsa has done (at Athletic Bilbao) is worthier than what Simeone has. Marcelo made a team out of nothing.”
Anwar El Ghazi - former player
"He is a little bit different, he can be very aggressive and shout at people but then he'll be very quiet.
"He pushes everybody to the limit, for example my body fat used to be 10% or 11% and now it's 8%.
"We train a lot, it's very physically and mentally hard. You do the kind of actions that you do on the pitch. We train like a realistic game, like passes you would do during matches, those type of things. Training is very different to what I experienced when I was playing at Ajax. We don't do position games and we don't do a lot of matches during the training sessions."