Baseball drafts arent like football, its not that rare for teams to draft first picks with players already set in at those positions in the majors. We're still talking about a kid whos just 18, with the Sox system he probably wont sniff the majors for another 4 years or so. A lot can happen from now until then. Sox still win if Pedroia and Ellsbury are showing no signs of budging at that time, that way if Dent is a a top prospect they can deal him off in a lucrative trade.
They even got Hunter Morris who's best position is 1st base, while Aaron Bates and Lars Anderson are both in Single A