Jonah Keri of Grantland on advanced pitching stats:
The idea behind FIP [Fielding Independent Pitching] was to strip out the impact of defense, as well as luck, official scorers, and other factors beyond a pitcher’s control. If a pitcher commits a two-out throwing error, then gives up seven runs, none of those runs are earned and none count against his ERA. If Terry Francona loses his mind and puts David Ortiz at shortstop, the countless balls that get by Papi (which wouldn’t be ruled errors) that a competent shortstop could normally handle wouldn’t destroy Josh Beckett’s FIP.
Like many things, this seems so fundamental now. I know that a lot of people hate advanced stats and argue they can’t tell you the whole picture, and that’s true, but they tell you a whole lot more than existing stats and the naked eye.
Keri runs down examples of bad signings that were masked by traditional stats, but would have been exposed with more advanced stats.