I will start telling you something I learnt a while a ago and after that we go for Leo.
When I was younger, like nine, my father introduced me to the rock music, he showed me some musics of Scorpions, Queen, Van Halen and others, I liked and it did not take long for me to get enter in rock universe with everything, Guns, The Police, Bon Jovi, Kiss, Black Sabbath and ect.
One day I was talking with a teacher of mine about rock and I asked him which was the best Rock Band Ever. He answered me directly: Bands come and go, you would've probably heard something like Metallica in others singers. You would also have heard teen bands like Green Day and Evanescence over and over again, but with The Beatles, this will never happen, you will not hear anything like this four again and for that, to me The Beatles is the best rock band ever, they are unique.
At that time I respected his opinion, but was very frustrated. I already had heard of Beatles, it was nice but best rock band ever? The answer of my teacher really intrigued me, I started check lists of Best Rock Bands ever and there was Beatles again, in each list I checked and Beatles was on, always in first or second. I started to take opinions of great musicians and almost all of them talked about Beatles, saying that the four was genius and unique. I really did not understand, so for a while really thought Beatles was overrated.
One day I gave a second try to the four British, I looked for the most heard songs and chose Hey Jude, I put the headset, closed my eyes and tried to enjoy. After a while, something strange happened. I already had heard Hey Jude, but this time it was better, I played it the third time and I could hear instruments that at the first time was not perceptible. Every time I heard the song it became more complex. I started to listen more and more of Beatles: A Day in Life, Something, Come Together, Yesterday; every music of the band had the same effect, the more I heard, more the song became more good and complex. It was like a puzzle, the composition of the songs was so brilliant that every time I discovered something that was unnoticed before and now the opinion of my teacher was making sense to me. The other bands like Green Day and Pearl Jam that I was accustomed to listening became more and more boring because they were so simple. The first time is the best time with these bands because is all already there.
With this experience I learnt something very important which is:
Quality is not easily perceptible and for it to be perceptible requires experience and effort.
I didn't liked Beatles at the beginning because I had not heard enough, I was not prepared for such quality, I was accustomed with much more simple songs, when I was exposed to Beatles with such a complex composition I was not able to enjoy, it is like trying to show the movie The Godfather to a child, he will get bored even the movie being one of the Greatest ever, the kid is not prepared for such quality yet.
This situation applies in everything, even in football, your question is why do many professional footballers and managers see Messi as the best player of all time? It is simple, they have more experience and are very perceptible toward the sport, they have been trained, studied and worked with football, they see what others can't.
People who like football think Messi is a good player, people who watch frequently the game think is one the best of his generation, but people who understand the game such as managers and former players know he is one, if not the most dangerous player ever.
Messi same as Beatles, is unique and we probably will never see anything like him again, but suchlike the Liverpool band is hard and requires effort for you to understand why and for that many people are not even aware that they are watching probably the best player ever.
When I started watching football I didn't understand why managers go so nuts for Messi, he could not do elasticos, step-overs, fancy passes, he did not make head goals and seemed always lazy in the field. I thought he was good but not one of the best ever. For me, Ronaldinho was much better, even Cristiano was more complete.
With time I became very interested in the sport and started to learn more about it. I watched documentaries about the game. I started to learn about legends such as Maradona and Pele, Van Basten, Cruyff, Eusebio, Romario, Baggio, Del Piero and Zidane. I started watching every match that I could and the much I learnt, more Messi was becaming impossible to me. I realized that the players I compared with him were not even close, everyone can do step-overs and elasticos, but to dribble four defenders as if playing with kids you has to be one of a kind. This fancy style of playing football was becoming boring to me and the real football with focus and objectivity was more enjoyable. What I thought was laziness of the little man was in reality strategy. Messi is a smart player, he sees the spaces, analyzes the game and does the right move at the right time, he doesn't need to run like a maniac.
I started seeing what others do not see, but only because I put an effort to understand the game better. Managers and former players see what I see too and much more. They know how puzzling it is to face Messi in a game, they know how diffucult is to mark a player who can score goals with three defenders in his back, a player that can solve a game in second either with a pass, dribble, shot or all combined, a player that has vision, dribble, pace, acceleration, speed, balance, finish, free kick, etc
Some players and managers already knew that Messi will be one the greatest before he is even be in the eleven of Barcelona. Recently Kobe Bryant spoke in news how Ronaldinho presented Messi to him, Dinho said to him : I will show you the best player of all time. Kobe replied: you, you will be the best ever. To this, Ronaldinho said no and than presented Messi to Kobe saying: Him, he will be the best player ever, Lionel Messi. He said this in 2006. Dinho saw something special in Leo because he is very perceptible toward the game. He played with R9, Romario, Rivaldo, Roberto Carlos. He is experienced and understands the game better than most people.
Managers and former players see a Messi that most of the people don't see. They can capture qualities that go unnoticed for most lovers of the sport and they know that Messi is a once in a life time talent. It has nothing to do with statistics, goals or titles, they knew that Messi was special even before all that records and numbers. Managers know that Messi is in an another level and is a level that is unlikely to be reached again.
Source :- Google