If we say Messi is Barcelona or Barcelona is Messi the two statement are right, and as a Barcelona fan I've always wondered the fate of Barcelona playing matches without fielding Messi.
I keep asking myself if those bottom and average teams in La Liga will still tremble at the mention of Barcelona or if other European teams that are paired with Barcelona in Champions League will still consider themselves unfortunate to be paired with Barca?
Barcelona will definitely decline after Messi eventually retires or when he moves to another club next season. Even now that he's still present at Barcelona, that has been a big decline in Barcelona's performance both in domestic league and European tournaments
As Messi is getting older, it's perfectly normal for him to decline in both performance and efficiency. Even though he's still that player that can dribble and destroy any defence, this will continue to decline over time
He has been a crucial role in Barca for more a decade and if he finally takes the exit door or retires, the great impact will be felt. It doesn't matter if good players are recruited to fill the vacuum
Imagine what happens in matches when Messi is half-fit let alone what will happen completely out of the team
My fear is that Barcelona will not decline like Manchester United when Messi eventually leaves