Hiura is a 6'-ish former 2B that possesses one of the best hit tools in this draft. He's hit everywhere he's been, from his high school senior year to two years at UC Irvine to last summer on Team USA. He's also towards the top of the leader boardsthis year in batting, walks, on-base percentage, and slugging. He's got a short, compact swing with a ton of bat speed, not to mention a pretty good eye at the plate and great bat control. Scouts high on Hiura say he has a plus hit tool with future plus power.
However, he hasn't played the field in over a year, hampered by an elbow injury. On Team USA he served as their DH in games and does the same for UC Irvine. There seem to be growing concerns that he'll need TJ surgery soon after being drafted/signed. This doesn't help allay defensive concerns, especially since his arm wasn't all that great even before the injury and will most likely end up fringe average at best and below average at worst. He's played in the OF (CF and LF, specifically) before his arm injury MLB.com suggests playing him in LF so he gets to the majors more quickly as the say he would need work to keep him at 2B.
However, despite the injury and defensive concerns, I think the Sox believe in his bat and that's why they'll draft him if he's there. Keith Law has stated there's some industry talk connecting Hiura and the Sox already, plus he's been mocked to them on several sites including ESPN and MLB.com. The only reason they wouldn't draft him is if he's not there, which is still a distinct possibility as college players who have a long history tend to get drafted high and a team might grab him in spite of everything. However, if he's there at 24, he'll be the pick.