In a couple of places I've seen both Dayton Moore and Chris Antonetti named as potential replacements for O'Brien. Personally, I think either would be great choices -- I followed the Red Sox GM replacement pretty closely and came away impressed with the credentials of both assistant GMs.
However, both Moore and Antonetti, while initially in the running for the GM spot in Boston, took their names out. Whatever their reasons may have been (it's rumored that Moore has been promised the Braves GM position after John Schurholtz retires) why would either of these guys choose the Reds position if it's offered to them over the Red Sox position.
I realize that the knee jerk response to this question is that "we don't have a lucchino" and that they could then have total control here. But is that really enough?