People seem really concerned about a number of things - some genuine, some not so
Genuine concerns are those about his age - Messi at 33 is still the best player on the planet. However age catches up with everyone, but at Barca he plays all the time. With us I dont think he would - I think there would be rotation to help save his legs (I dont actually see that as needed at the moment - he still looks as good as ever). He will also have a very different team around him - KDB, Foden Jesus, Sterling, Walker - players who just run and run all match and will cover the extra ground.
He wont affect Foden's progression - infact if you asked Phil himself about the prospect of playing/training with Messi every day - what do you think he would say - He has just finished playing next to Merlin every day - listen to what he says about him and now he has the prospect of playing/training with Messi - do you think he turns that down? What about the likes of Doyle, Braff etc etc
Genuine concern about cost and wages - the club will know if this is feasible and we have to trust them (despite what the press/media will say).
The dressing room/control/influence - he wont be capt - I think this will fall to KDB this year and the next few years. There are some very strong charachters in that dressing room who have been here a long time - Ferna being another, Walker as well besides KDB. There is also Ake who was capt of Bournmouth who obviously has leadership qualities (not sure about Koulibaly should we get him but he would be another very experienced player) - Messi, despite who he is will be the new boy so to speak. Then there is WHO runs the club - Khaldoon and Txixi (whom he knows and will have a good strong relationship) - do you believe they will allow anything to affect the club - UEFA just tried it and got woman slapped!
the we come to the non genuine concerns:
Media/opposition fans/teams - fuck them! Who cares what they say. As fans we shouldnt care less. I sense that people are scared/worried that if we lose a game/league/cup with Messi in the side the backlash will be stronger - are people not strong enough to face that? Jesus, we have faced worse than that over the years as city fans. Barca lose with Messi in the side, Juve lose with Ronaldo in the side.
He is still the best player on the planet