Team Defense, part 1

Measuring defense is a very difficult thing to do. Statitically minded people have been able to deduce hitting to it's very basic parts and put a specific run and win quanitity to every swing of the bat. Defense, and the pitchers who benefit from it, is much harder to measure.

Every defensive discussion in baseball must begin with some baseball theory. The end goal in baseball is to win. Winning is 50% run scoring and 50% run prevention (this is actually disputed, but for now let's assume that it's basically true). A team's ability to prevent runs is divided between the pitcher and the fielder. The vast majority of the ability to prevent runs lies in the pitchers - especially in their ability to prevent home runs, walks, and strikeouts. Pitchers control probably about 80% of run prevention - or 40% of winning games. The other 20%/10% lies in the hands of the fielders.

The second thing that needs to be said in regards to theory is that virtually every major league fielder is very good at their job. This may be the one area where baseball is not about failure. Jason Giambi would be a dominant defensive player in a high school baseball league. He has the training, experience, and physical skills to do so. Bernie Williams has a pretty strong armed when compared to most Division I outfields. The differences in major league players are very subtle. The best defensive shortstop would struggle to make two plays a week more than an average one.

There are a lot of different ways that we try to measure defense. The typical, dare I say "mundane" way of measuring defense revolve around the statistic "errors". Errors may be the worst statistic in baseball. Errors are subjective (it's up to the official scorer's decision) and don't tell us anything (If Derek Jeter boots a ball, he gets an error, but if he simply doesn't get to the ball, there is still a runner on 1st base, but the player gets a hit). Errors are good for determining if a batter gets credit for a play or not, but does a terrible job for fielders.

The best statistic, in my mind, for determing team defense is Defense Efficiency Ratio or "DER". DER is really simply. It takes the total number of outs made by a team's defense (not counting home runs or strikeouts) and divdes it by the total number of balls in play. The Yankees were pretty good last season by DER. DER listed them as 8th in the majors with a .7108 ratio. Only the Tigers in the AL were better.

Great, the Yankees were pretty good last season. The problem is that most individual (looking at the single fielders) statistical systems thought that we were actually pretty bad. There are a lot of ways that people use to attempt to measure individual defense. David Gassko tried to predict the number of plays that a player should make based upon how many balls fell in to that side of the infield. Zone Rating divides each section of the field in to a player's responsibility, and John Dewan of The Fielding Bible uses a +/- system based on individual play locations.

All three are great attempts at determing range, but all three have their problems. They don't account for defensive positioning or shifts. They don't account for ballpark nuances either. All three also peg virtually every Yankee defender at below average or worse. This doesn't line up with what we see with DER. Tomorrow, I am going to have a look at the actual numbers and see if the Yankees indeed have an above average to good defense, or a below average or worse one.