While reading the New Bill James Historical Baseball Abstract, a curious similarity between football and baseball defense struck me. James discusses the difficulty of analyzing baseball defense, especially the effects of the pitching staff and how a field full of great defensive players will produce just as many outs as a field with slow-footed DH’s. Just as in baseball, football players compete for a certain number of sequence-ending plays (outs in baseball, tackles in football). Similarly, defensive statistics are influenced by an independent factor, the groundball-flyball tendencies of a pitcher or the run-pass tendencies of an opposing offense. Not surprisingly, fly balls and passes are similar. Both come down to a single defensive player (a defensive back or an outfielder) and mistakes are most costly on these plays. Groundballs and running plays also share characteristics: multiple players are necessary and speed is tested in the offense. Many statistics are similar. Defensive backs are rated on their interceptions, outfielders on their putouts. Therefore, in both analysis and statistics, football and baseball defense is very similar.
