As I said months ago, it's either a R9 move or Umtiti move
Right now he is taking the second road.
This surgery is scary for every player, you're never the same after it, he may have to completely change his playstyle after it ... and it take a lot of guts.
After been under the knife 3 times he is going the safe option (aka the Umtiti way) is to wait and hope for a miracle, milking the stupid contract as long as possible and saying good by to any hope for a decent career.
Now FCB has to identify exactly why all of this replaces are happening, with 20 years old Messi it was clear : exhaustion as he was obsessed since la Massia to play every minute and his carnivorous diet; he fixed the second one and the rest was history.