Declan Rice

No harm whatsoever, midfield is where we are weakest (or at the very least, we are weaker there than CB). Without going all Johnny Giles on the subject of midfielders, there isn't any particular reason why he should be confined to sitting in front of the back 4 either. He's a young fella, he's reasonably quick & strong, he can play football & pick a pass-  no reason why he can't be a box to box type, or the one in the centre who drives forward with the ball. 

A fit McCarthy is probably more suited to the sitting/defensive role anyway, but I don't see any point in trying to limit what Rice could be capable of (and I accept we don't know the full range of his capabilities or limitations yet either) by boxing him off as a defensive midfielder. 

I'm not even sure that what Moyes does with him will have a huge bearing on where MON plays him, given our lack of decent options in midfield. Going back a bit, Jack played the likes of Lawrenson & McGrath in midfield on occasion even though they were far better footballers and defenders than McCarthy & Moran, McGrath only went back the way for Ireland as a result of a combination of Townsend's emergence and his own injuries/age meaning he didn't have the legs for midfield any more. Trap played Kilbane at LB & occasionally centre mid before he played either position for his club.

MON has tried (& failed miserably) to make McClean into a left wing back, a centre mid, a No. 10 behind the front man and a centre forward at various times, despite all evidence concluding that he can only play in one position. He has also moved McCarthy from a defensive midfield position to an attacking one on occasion (jury out on that one too) so I think its likely he might be up for a bit of experimentation with Rice's position too. 

"It's going to be pretty difficult as he's Irish," Keane said. "Where else would he want to go? It's pretty straightforward. He is Irish."