That raises a question: what is the hardest position in football? And why?
Difficulty is relative but most accountable players are surely center-backs and keepers.
Looking at Palacio for example. His past twelve months have been pretty abysmal. Yet, as far as I've seen, he plays often enough. This is probably based on the perception that he has the ability to eventually score. Heaps of other strikers fall into that category.
It's a contentious point but you might say that the equivalent of a striker not scoring goals is, for a defender, mistakes which lead to conceding goals. The latter puts you under far more scrutiny than the former.