Jeter's defense on the decline - Yankees Blog - ESPN New York:
"Basically, what this means is that Jeter has made seven fewer plays than the average shortstop would have made, on balls hit to the left of where a shortstop would play. Or in simpler terms, Jeter is missing out on some balls that are ending up as base hits to center field.
That's shows signs of decline from the previous two seasons in which Jeter was rated -1 (2008) and +2 (2009)."
Repeat after me. "Just because you have found a way to measure something doesn't mean it has a predictive quality."
Or more simply, "Defensive metrics are useless."