The biggest lie told by NFL general managers is that their sole motivation for picking a player was, “He was the best player available.” Player evaluation is not precise. You can’t say one player is 1 percentage point above every other player available. Every good GM puts players into categories because they grade out as potentially equivalent.
Smart GM’s find “difference makers”; players that could eventually be considered All-Pro’s, or sometimes better yet, just below that level, so that the team does not need to pay the accompanying bonus. But finding 10 great centers does not make a Super Bowl contender.