Here are two pages from fangraphs UZR. In short it takes a lot of factors; Saving runs with your arm, double plays, range runs, error runs, park factors, etc. http://www.fangraphs.com/library/defense/uzr/ http://www.fangraphs.com/blogs/the-fangraphs-uzr-primer/ Here is the current MLB UZR leaderboard. Gomez is currently tied for 1st. Kind of puts into perspective the year he is having. Not only is he having an awesome offensive season, he continues to be a top tier defensive player. http://www.fangraphs.com/leaders.aspx?pos=all&stats=fld&lg=all&qual=y&type=1&season=2013&month=0&season1=2013&ind=0&team=0&rost=0&age=0&filter=&players=0&sort=23,d I think you need to reread your links a little more carefully. In particular "Does UZR tell us what actually happened on the field?" UZR has flaws but it is probably the best we can get right now. It would be nice to know how well a player fields balls depending on where they are positioned. Basically buckets with the player position as the center. Then another stat so you can tell if the player has good defense based on positioning or talent.