We could have probably coped with the injury of our most important player Quag but the redcard by Melo came in the worst possible moment and the mentally weak team collapsed (btw one of the main reasons for the psychological weakness of our team in Melo).
The entire team having a poor mentality is certainly not Melo's fault and he can't be held accountable for them not being able to handle
Parma and conceding
four goals. Even if we played with nine players that should never have happened. The next next three games, again, shouldn't have been much of an issue if Melo was nothing more than a "good player" (read - interchangeable). After all, we had a supposed-leader in Marchisio waiting to step into his favoured CM role, no?
Saying he's one of the "main reasons" for the team being mentally fragile also makes no sense. His absence should have strengthened the team according to this view.
Trying to rest the blame for the team's implosion on this guy's shoulders only suggests he is (was) an essential player.
Simply "good" players aren't essential unless their alternatives are literally ball boys or something.