well but what about this guy http://www.chicagotribune.com/media/alternatethumbnails/story/2011-09/23456406441600-20145204.jpg well sure, all baseball data is accumulated through observation. my issue is that, to my knowledge, there is no standardized system in place to accurately record EVERY activity on the baseball field a la pitch f/x (but not just for pitches). while we can certainly watch video and observe a player's reaction to a batted ball and how long it takes that fielder to throw the ball from the moment he receives it, so on and so forth, that activity is not quantified in a standardized way to allow for comparison and analysis amongst an entire field of other comparable data points. furthermore, gauging anything by radar gun, and especially the naked eye, simply doesn't provide the level of accuracy and comparability required. those tools might serve the purpose of a scout, but for those looking for information that isn't colored by the fallibility of human observation, it simply is not good enough. You'll never get that point though, even with pitchers and hitters. There's too much luck and variables even with the more advanced data with pitching and hitting. The goal is to get the best with what you have and right now, defense still requires that human element.