The guy who blogged it speaks about Duncan's surprising numbers: "How is that different from Dewan’s plus/minus? His plus/minus is essentially the same as UZR if you turn it into runs. The only significant difference is that it uses a different database, which seems to make a big difference. Duncan was a -6 last year in 86 games, so between this year and last, he is +3 net runs in 119 games. I am sure that the 95% confidence interval for 119 games would be like plus or minus 15 runs or so. As I always say, when you have a group of sample data, if there are not the usual outliers (whatever you would expect when you combine a bunch of bell curves), you are likely cheating. Then again, we can’t just assume that every player who does not comport with our notion of that player is an outlier, otherwise, what is the point of the metric in the first place? What we do is to regress the metric towards some “scouting” report on the player. If that “scouting report” is a knowledgeable player watching a lot of that player, that is fine. But, again, we have to be careful and understand that these metrics are generally better than our “minds and eyes” which can play tricks on us. The metrics are (hopefully) unbiased. We also have to understand that the larger the sample that the metric is based on, the more we have to rely on it, at the expense of what we “think we know” about that player (assuming that the metric has some requisite level of accuracy and reliability of course). Duncan has some kind of a bad reputation as an OF’er, and I know he looks awkward out there, but LaRussa has said that he is actually a very good outfielder. Whether Tony was just being kind or PC, I don’t know. But when I think of Duncan, I always think of Tony’s remarks about his defense. If I had to put a value on his defense, I would honestly say it was just a little below average (of course, with a lot of uncertainty) . I get that estimate from his general rep (bad), his UZR (a little above average in 119 games), and LaRussa’s statements (which I interpret as being that he is average at worst)."