Maybe we would, maybe we wouldn't. Herrera played just few games deeper in central midfield for us, with mixed performances. We definitely will be with Fellaini. Fellaini played many more games in central midfield and is usually terrible whenever he starts there, and not just that, my biggest gripe with Fellaini is actually that we are terrible defensively when he plays in cm, our defense is always exposed with him.
I am not sure that anyone is saying that Herrera is excellent or something like that, even I as his fan ackonwledge that he is having quite shit season, but he is still much better option than Fellaini. Fellaini simply isn't good enough to be a starter for us, and never will be, I am quite sure many people would pick Rooney in midfield two ahead of him, especially alongside Schneiderlin.
And also many people want Herrera there simply because then we could pick other players over Fellaini in number ten role, and not just because they want to see Herrera played there.