He was the best performer in the squad in two of the last three seasons, prior to this one, and so was over that three year period quite easily the best player in the team overall. Basically, the consistency you say you want from him, he has already shown.
Also his level last year was quite special really. Hopefully he can return to those heights but his level of the two years prior was, though not as high, of the calibre required.
Shaw is the very last player in the current squad who can be tarred with the inconsistency brush really. Poor starts, poor periods and poor seasons can happen, for many reasons. He's been crap, but the new manager coming in is exactly the kind of thing that can see a player turn that around.