They don't exclusively draft for need. People here are implying that because they need a tackle, Brad will automatically draft a tackle for the sake of taking one. I don't believe he will unless it aligns with his draft board and player valuation. He will take the best player available on his board, that potentially aligns with a need, assuming that player grades out where he wants them too. Again, he'll likely have a board that grades out players with first round valuations and other metrics. only so many players will have a first round grade on his draft board. If we get to #17 and a tackle isn't one of those guys, I don't believe he'll take one for the sake of it, simply out of need. If a tackle is drafted at #17, it likely means Brad has a first round grade on them and they were either his BPA on his board or very high up on it.
Also, as NY Lion said, Brad is also unpredictable, and could draft anyone. Who predicted Holmes taking Jaymo, Gibbs, Campbell where he did in the draft?