BPA is a very theoretically thing. How do you compare a Center with a small D? It is all not so easy, and I think the current Roster and Prospect pool is mostly always in mind of the management when they draft in the first round.
Really? And do you have anything to support that assumption? Because as far as I can tell, there's a consistent lack of any such correlation in the top end of pretty much any draft I can think of.
2010. Positional needs, was it? The Oilers, whose two best prospects were wingers, taking Hall? The Bruins, completely loaded at center, taking Seguin? the Panthers, whose previous two 1st rounders were defensemen and who hardly have anything serious up front either in the squad or among their prospects, Gudbranson was their logical "team needs" choice?
2009. Tavares-Hedman-Duchene. Funny, that seemed to be the expectation all year long, irrespective of which teams ended up with those picks. And what do you know, that's how it panned out.
2008. Stamkos-Doughty-Bogosian. Consensus lineup, nobody made any unexpected choice over "team needs".
2007. Ditto. Kane-Vanriemsdyk-Turris, none of whom particularly responded to any clear "team needs" and none of whom were the least bit unexpected.
2006. Johnson-Staal-Toews. Johnson was the consensus number 1, for the next four there was no clear pre-draft order. But was another center really the obvious choice for the Penguins need-wise, rather than for example a goal-scoring winger like Kessel? And did Toews at that time fit the Hawks "team needs" in a way that f.e. Backstrom didn't?
More importantly, can you point to anyone from the management of any of the drafting teams saying anything in retrospect along the lines that they made their choice because their guy was the type of player they were looking for?
Fans love the notion that teams draft according to need. They love it because it enables them to pretend that drafting decisions take place according to a logic that they can take part in, discuss and predict. Mock drafts feed that illusion, because they argue as if that was true. But the fact is that if you look at actual drafting decisions in the first round, they more usually than not fail to make any sense from that perspective. Sometimes a certain philosophy plays into it and sometimes teams are looking for specific things (if not neccessarily in the first round), but by and large I would argue that there is no discernible rational pattern to drafting that allows anyone to form any meaniingful prediction or expectation without knowing in detail and specifically how each team sees each individual prospect - that's what it ultimately comes down to, which is of course no fun at all. Every year you read how this or that player is exactly team x's kind of guy, and every year, team x pass him over nine times out of ten. Every year, there are quite a few first-round picks that not only fail to address the obvious needs, but which fails to make any sense at all from that perspective. Was another skilled Russian forward really the Caps biggest need last year? LA really needed to supplement the league's best young defense with yet another blueline prospect? The Blues and Rundblad? They needed him so much they traded him a year later, citing the reason they had no room for him. Sit down if you like and sort the first round, matching each team to likely available players and according to their "team needs". You're not going to get much of a correlation with the actual result. The main correlation you're going to get is with pre-draft ranking, and the second strongest you're going to get is with nothing predictable at all. The first of these is "BPA" insofar as general rankings manage to predict who that is, the second is individual team assessment that none of us essentially can know anything about.
"How do you compare a Center with a small D"? I'm pretty sure that what you at least
don't do is say "Aw shucks, there's no good way to compare physical domination and offensive production anyway, let's just take the one that makes positional sense". However difficult and imperfect the comparison of different kinds of players are, it is and remains what scouting and drafting comes down to in the end.