Good post.
@Zehner, just look up his goals for Southampton. Of course he wouldn’t score as many, system, coaching and the fact that he’s playing alongside some of the best players in the world surely has a huge impact. I do believe you didn’t notice him much for Soton’ though, he created goals out of nothing and scored a lot of great goals.
I'm not really sure what that shluld prove, to be honest. Initially this debate emerged because I said that Hazard would be better than Mane in that system.
Mandzukic role didn't change when moved to the wing, his role was still to press and be a target upfront, Fabregas was a failure and Henry played as a winger/inside forward for many years from his Monaco days to the end of his career. Lahm is basically your example but it was a role that fitted with his qualities and mentality.
As for the Klopp part, it highlights your failure to understand the point. Klopp turned Pisczek into an attacking fullback because it fitted his natural game, Salah was a goalscoring wide player as his 14 and 15 goals in consecutive seasons in Serie A. He also didn't shift Milner to the middle from the wing out of nowhere, it's something that Milner had already done for Villa and City but most importantly within Liverpool's system it fits Milner's qualities because they have a crucial role of covering in the width behind their very attacking fullbacks which is perfect for someone that has played as a wide midfielder.
And you are the one not thinking about skillset, I talked about role and you think that it means position when it's about how you play the game and why which is linked to skillset and mentality. In your mind it seems that a role is just a spot on the field when it's not.
Don't you think you're dismissing those examples a little bit too easily? I mean, you're explaining me that the roles as a left winger in those two systems are vastly different to each other but when I name youna striker that Klopp turned into a right back you are all like 'what? He wanted an attacking fullback, that' s why' as if it was the logical choice in such a situation and quite common practice.
See, a role for me is how you interpret a position. Which runs you make, where you position yourself in possession, how you work against the ball and which decisions you make in certain situations. Pisczek was not only a switch of position but also in role because he had to learn new runs, adapt his decision making and so forth. In a system that grants players much freedom, those roles are usually defined by a players nature but coaches so obsessed with tactics as Klopp or Guardiola grant only a minimum of that. They instruct you how to behave in the build up, in pressing situations, after losses of possession and so forth.
So no, a footballer is no robot that can be controlled like a FIFA character but he's a human being with the general ability to listen to and execute instructions he is given. Of course it doesn't make sense to buy a player only to tansform him completely and most importantly, the role he can occupy requires a certain skill set he should have. But Hazard has played the same position, the changes he'd need to make to his game are anything but undoable. Would he play like Mane? No he wouldn't. Would he play like Chelsea Hazard? No he wouldn't. It would be something new and the question is if it was better than the current version - and I'd say yes. You mention Salah's goal tallye. Hazard has constantly scored ~15 goals in the EPL although he was occupied in the build up of Chelsea's attacks much more than he would be in that Liverpool team. His numbers would most likely skyrocket since he can pick up much more easy goals and would find himself in many more one on ones or situations in which he has space to attack.
And as good as Mane is, Hazard is one of the very, very few players who would be a clear improvement on him. Mane may have a little bit more end speed but Hazard is practically undefendable in one on ones. I understand if you see that differently and IMO that's the actual debate, not the stuff abou roles and positions: Would Hazard's skill set allow him to be even better than Mane in Liverpool's system? And to me, the answer is a strong yes. I'd be thrilled to finally see a player of such calibre under Klopp because IMO, he hasn't had a player of Hazard's ability in his teams up until now. And when you see how he makes every player punch above his weight, sky'd be the limit for Hazard.