Scouting report in a nutshell: 21 year old SS with a fantastic glove and a light bat. Could use to draw some walks, makes decent contact, not really much power to speak of.
He's your basic "defend a lot, hit enough not to embarrass the team" player and would probably draw some fire in Boston for the lack of hitting, but by all accounts the glove is real and is at the major league level right now. If the consensus is that with a bit of experience the hitting might come around Diaz could make something of himself.
I guarantee you every Sox fan forum in the world would spend every single offseason Diaz spent in Boston arguing between the defensive spectrum folks making points about how he made the pitching better and fans who watch baseball for the offense trying to figure out how to get a SS who can hit.
My question here is basically that: do you see Diaz playing a role in Boston's future or is the guy just not a fit in a town that demands that all of its position players swing the bat well?