Bill James on Fielding, Part 4

Of the 243 Win Shares and Loss Shares which are attributed to pitchers and fielders on a team, 162-game schedule, about 60 to 70 typically are assigned to fielders. The percentage used to be much higher, because fielding used to be more central to the game.  The split between pitchers and fielders depends on the team’s strikeouts, walks, hit batsmen, home runs, errors and double plays. Strikeouts, walks and home runs make the fielders irrelevant; there is nothing the fielder can do about those things.   As those things increase, the "pitcher’s percentage" increases. Similarly, errors and double plays are actions essentially of the defense, to an extent outside the control of the pitcher, so as those things increase, the "fielding percentage" increases.

In modern baseball strikeouts are, of course, at a historic high, and errors are (always) at historic lows.   Home Runs are not at the level of ten years ago, but they’re not at the level of the 1920s, either; in 1925 the average major league team hit 73 home runs, whereas in 2014 the average team hit 139 home runs.  The three-cornered battle between hitter, pitcher and fielder is gradually being smushed into a two-man battle between pitcher and hitter, with the fielders increasingly taking on the role of innocent bystanders.