Mikhail,
I have a different view on Miguel. He seemed to be one of those adventurous full-backs who loves going forward. And his blistering pace can be a weapon, IMO. Nonetheless, his defending is solid, and he is able cover ground because he has such a good athleticism.
One of the drawback is, of course, he is extremely raw. His crossing needs some refining, but other than that he is quality right back, IMO.
BTW, Ferreira is way overrated IMO, and not even worth half the amount Chelsea paid. Only player who rivals him, IMO, in terms of unwarranted reputation is, surprise, his former teammate Deco.