That is just silly. Carrick is a little sluggish getting off the mark, thus you don't need pace to play in his position according to you - you can be much slower even, but you fail to take into account him being world class in anticipating passes and intercepting as well as his ability to dictate.
Neville was no Valencia, but he was much faster than Blind. When he got as slow as Blind he quit. In addition to being faster and stronger and tougher, his awareness,tackling and positional play was much,much better. When Blind doesn't excel in any of those areas, he is too slow to play fullback for us, just as I fear he may lack too much physically to play cdm for us as he doesn't excel over others enough in other areas.