"Best available" is always a subjective argument that leads nowhere. But I am pretty sure the consensus of opinion is that Darling was best available, not Pitt. And media speculation didn't have Ballantyne taken where we reached out and plucked him, but he met a pretty specific need for the club.
There are a heap of variables that come into deciding who is the best available, and especially in the debate about smalls vs talls. It is speculative and a cursory glance over the re-dos of drafts from years past shows that. I would be pretty sure that selecting Palmer at such an early pick over that years #17, Harry Taylor, had as much to do with our need for a hard running inside mid and the lack of need for a KPD as it did about best available.
I think there is a tipping point in drafting where the difference in "best"-ness becomes marginal when weighed against needs. It is why the draft is unpredictable after the first 10 or so selections. By pick 17 that is well and truly in the realms where picking for need comes into play when deciding between a highly rated small and a highly rated tall. We certainly won't be taking a ruckman even if they are rated best available, and I am tipping a small forward won't be on the cards regardless.
This was my point, hence the quotations used. Pitt would be the classic case of the more talented and perceived 'best available' player over the immediate need that Darling would have been. He was touted as a top 10 pick and an absolute steal at pick 20, whereas Darling was seen as having already hit his ceiling having been a man playing against boys, he was always going to slide. This directly plays into your point though and thus shows one clear perspective of going with the 'best available' approach.
As for Ballas over Swift, he was a 2nd rounder of which the speculated best available is a little harder to gauge, but he did appear to be more of a take or be taken pick, and one certainly needs based which again chalks up another for the needs over prospective 'best available'.
Palmer/Taylor - It's pretty easy to go that far back with the benefit of hindsight, we were always going to take Palmer with our pick. It was either him or Myers but he was taken just before our pick. Taylor was never in the picture for us having been taken 10 spots later than Palmer. I don't remember Key backs being the pressing need at the time though? All I remember was that our midfield was shown up as too small and too old in 2007. Our backs held valiantly under the barrage they received at the hands of the Palmer/Bell led midfield. Would this point still have been raised if we took for instance a Paddy Dangerfield, probably not.
I guess there really is no distinguishable more successful method, there will always be contraries to the rule. Often drafting on needs is seen as reaching and 'underselling' your position in the draft by not taking the player you deem that 17th best player in the draft. I bet Richmond wishes they didn't reach so high for Conca and just took Dyson Heppell with their pick, Conca's been sent to play the same role down at half back for which Heppell is clearly the better fit, but thems the breaks I guess. You make your decision and you have to live with it. I'd hazzard a guess without insult to Conca, it'd be harder to live with the reach of taking the lower rated player and failing than taking the player deemed the best at that spot and failing.





