**Component 4: Balls in Play**

Components 3 and 4 are calculated together. After Components 1 (stolen bases) and 2 (wild pitches) are accounted for, Components 3 and 4 are evaluated by calculating the expected value of the plate appearance, based purely on the basic result – walk, strikeout, or ball in play – assuming average results following the play. If the batter does not put the ball in play, the results are credited to Component 3. If the batter does put the ball in play (including hitting a home run), the results are credited to Component 4. Component 4 decisions are calculated assuming average results based on where and how the ball is hit. Whether the ball becomes a hit or an out is allocated in Component 5.1. Calculation of Component 4 Player Game Points

As explained in the description of Component 3, Components 3 and 4 are not individually constrained to 0.500 winning percentages. Instead, the combined winning percentage of Components 3 and 4 is equal to 0.500. Overall, recently, putting the ball in play is a net positive event for the offense. Since 2000, the overall Component 4 winning percentage for hitters was 0.550.

In sabermetric circles, it is fairly common to distinguish between home runs and other balls hit into play. In fact, frequently, the term “balls-in-play” or BIP is used to denote those balls that are hit into play excluding home runs. The logic for this distinction is most apparent in the study of Defense-Independent Pitching Statistics, or DIPS.2. Home Runs: Component 3 or Component 4?

The basic idea behind DIPS is that pitchers have more control over those events which do not involve fielders and, of course, home runs (not including inside-the-park home runs) do not involve fielders. In a way, however, this breakdown doesn’t really make intuitive sense and has, I think, contributed to a lot of the misunderstanding and understatement of the effect pitchers have on balls in play.

Do pitchers have any control over balls in play? Several years ago, Voros McCracken developed a theory (called DIPS) that said that the ability to prevent hits on balls in play (excluding home runs) was the same, or virtually the same, for all major-league pitchers. His key conclusion was that one could predict a pitcher’s earned run average (ERA) for the next season looking only at that pitcher’s strikeouts, walks, and home runs allowed and that this predicted (or DIPS) ERA was, on average, a better predictor of future ERA than actual ERA. In other words, pitchers who had actual ERAs better than their DIPS ERAs would expect to see their ERAs get worse the next season (move toward their DIPS ERAs), while pitchers who had actual ERAs worse than their DIPS ERAs would expect to see their ERAs get better the next season (again, moving them toward their DIPS ERAs). McCracken’s conclusion that DIPS ERA was a better predictor than actual ERA was, and almost certainly still is, fundamentally true.

Some baseball fans have taken this argument a step further (some might say they’ve taken it to its natural conclusion) and argued that pitchers have no effect on balls in play. With all due respect, anybody who has watched baseball for any length of time knows that this argument is simply not true as I have just stated it.

Some pitchers are “groundball pitchers”. That is, the balls which are hit off of them tend to be ground balls, not fly balls. In the recent past, well-known groundball pitchers have included, for example, Brandon Webb, whose ground-ball percentages (percentage of total balls-in-play allowed that were ground balls) ranged from 61 – 66% from 2004 – 2007; and Chien-Ming Wang, whose ground-ball percentages ranged from 59 – 64% over the same time period (actually 2005-07; he didn’t pitch in the majors in 2004). On the other hand, Barry Zito’s ground-ball percentages over this same time period ranged from 37 – 42% and Curt Schilling’s ranged from 34 – 42%. Suffice it to say that I am not aware of anybody who would seriously argue that Webb, Wang, Zito, and Schilling’s ground-ball percentages are entirely the product of luck over this time period. So pitchers clearly have some impact over balls-in-play, right?

This is where the treatment of home runs becomes critical. Since 2003, an average ground ball was worth 0.0093 wins to the defensive team (i.e., to the pitcher). Over the same time period, excluding home runs, an average fly ball (including infield popups, excluding line drives) was worth 0.0138 wins to the defensive team. These results are relatively similar and, moreover, are relatively small. Compare these, for example, to line drives, which have an average net win value of -0.0241 wins to the defensive team or strikeouts, with an average defensive net win value of 0.0218.

But this is where home runs come in. As even McCracken noted in his original DIPS formulation, pitchers have some control over whether batters hit home runs against them. But a home run is just a fly ball (or line drive) that goes farther than the fly balls that stay in the park. As McCracken himself said, “Aside from walks, there are two basic outcomes for a pitcher: batter hits the ball or batter strikes out. With the latter, the result is almost always an out. With the former, all sorts of things can happen, including a base hit.” Of course, one of those “sorts of things” that “can happen” when the batter hits the ball is that he could hit a home run.

If we add home runs, which have an average net win value (to the batter) of 0.1382 wins, to the fly balls allowed by pitchers, we see that, all of a sudden, a fly ball allowed isn’t a slightly better outcome than a ground ball allowed (0.0138 wins to 0.0093 wins above) but, in fact, is a net negative outcome for a pitcher: -0.0032 wins.

Based on this, I allocate wins and losses attributable to home runs to Component 4 rather than Component 3. Since Components 3 and 4 are calculated simultaneously, however, this is, in fact, a purely semantic decision. If one were inclined to include home runs as part of Component 3, one could do so by simply re-defining all Component 4 decisions resulting from home runs as Component 3 decisions instead.

Overall, from 1921 - 2018, Component 4 decisions account for 34.8% of total Player decisions, 37.9% of all Batting decisions, and 55.6% of total Pitcher decisions.

Component 4 leaders are shown here.