As Sports Illustrated recently noted, analysts have come a long way in their ability to measure defensive quality. Even 10 years ago, defensive stats were like first-grade finger paintings compared to the Van Goghs we had for measuring offense. But no longer. My favorite system of defensive statistics is John Dewan's +/- rating, which he created for his excellent book, The Fielding Bible. Dewan's company, Baseball Info Solutions, actually reviews every play made by every MLB defender and compares each one to a database of similar plays. The system then counts how many unusually good and how many unusually poor plays a defender makes. The difference between the two is expressed as a +/- rating.