Baseball Player Won-Loss Records
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Component 9: Baserunner Advancement

In the ninth step of calculating Player Wins and Losses, batters, baserunners, and fielders are given credit and blame for baserunner advancements.
1.    Calculation of Component 9 Player Game Points
Component 9 doles out credits/debits for whether any baserunners (including the batter) advance above or below expectations given the type of play (hit, out) and the location and hit type (if available). Component 9 Player game points are allocated to any baserunner on third base first, followed by any baserunner on second, followed by any baserunner on first, then, finally by the batter. Component 9 accounts for 6.0% of total player decisions, making it the fourth-largest component behind Components 3, 4, and 5. Component 9 is the largest component of baserunner player decisions, accounting for 38.1% of total baserunner decisions. Component 9 is the second-largest component of fielding decisions for both infielders and outfielders, behind only Component 5. Component 9 accounts for 10.5% of total fielding decisions for infielders (excluding pitchers and catchers) and 22.4% of total fielding decisions for outfielders.

2.    Impact of the Batter on Baserunner Advancements
Component 9 Player Games are shared between batters and baserunners based on the extent to which player winning percentages persist across different sample periods. The mathematics underlying this division is described elsewhere.

To summarize, one measure of the extent to which a particular factor is a skill is the extent to which a player’s winning percentage persists over time. To evaluate the persistence of skills, I fit a simple persistence equation which modeled Component 9 winning percentage on even-numbered plays as a function of Component 9 winning percentage on odd-numbered plays:

(Component 9 Win Pct)Even = b•(Component 9 Win Pct)Odd + (1-b)•(WinPct)Baseline

where (WinPct)Baseline represents a baseline winning percentage toward which Component 9 winning percentages regress over time.

Equations of this type were fit for Component 9 Player Game Points for batters and baserunners. Separate equations were estimated for each starting base for baserunners. The results for these equations are shown below. A brief explanation of these variables follows.

The number n is the number of players over whom the equation was estimated, that is, who accumulated any Player wins and/or losses on both odd- and even-numbered plays. The value R2 measures the percentage of variation in the dependent variable (WinPctEven) explained by the equation (i.e., explained by WinPctOdd). The numbers in parentheses are t-statistics. T-statistics measure the significance of b, that is, the confidence we have that b is greater than zero. The greater the t-statistic, the more confident we are that the true value of b is greater than zero. Roughly speaking, if the t-statistic is greater than 2, then we can be at least 95% certain that the true value of b is greater than zero (assuming that certain statistical assumptions regarding our model hold). The value of (WinPct)Baseline, the baseline winning percentage toward which winning percentages regress over time, is set equal to 0.500 by construction.
note: To be precise, I estimate unique Persistence Equations for every season, which use all of my data in all of these equations, but weight the data based on how close to the season of interest it is. The equations shown here weight each season equally.
Persistence of Component 9 Winning Percentage: Baserunner on First Base
Batters:  n = 49,965, R2 = 0.0381
WinPctEven = (19.37%)•WinPctOdd + (80.63%)•0.5000 (44.54)
Baserunners:  n = 49,017, R2 = 0.1177
WinPctEven = (40.64%)•WinPctOdd + (59.36%)•0.5000 (99.22)
Component 9.1 player decisions are divided between batters and baserunners in proportion to their persistence coefficients (19.4% and 40.6%, respectively), or 32.3% to batters, 67.7% to baserunners.

Persistence of Component 9 Winning Percentage: Baserunner on Second Base
Batters:  n = 44,601, R2 = 0.0004
WinPctEven = (15.37%)•WinPctOdd + (84.63%)•0.5000 (32.59)
Baserunners:  n = 43,082, R2 = 0.0225
WinPctEven = (18.27%)•WinPctOdd + (81.73%)•0.5000 (38.12)
Component 9.2 player decisions are allocated 45.7% to batters and 54.3% to baserunners.

Persistence of Component 9 Winning Percentage: Baserunner on Third Base
Batters:  n = 32,327, R2 = 0.0160
WinPctEven = (12.40%)•WinPctOdd + (87.60%)•0.5000 (23.09)
Baserunners:  n = 29,606, R2 = 0.0006
WinPctEven = (-5.67%)•WinPctOdd + (105.67%)•0.5000 (-9.637)
Surprisingly, to me, there is no positive persistence of Component 9 winning percentage for baserunners on third base. Hence, these player decisions are allocated entirely to batters. I guess the ability to score from third base on a sacrifice fly, for example, is much more a function of how far the fly ball was hit than of how fast the baserunner is.

The relationship between Components 8 and 9 is explored in a separate article.

Component 9 leaders can be found here.

All articles are written so that they pull data directly from the most recent version of the Player won-lost database. Hence, any numbers cited within these articles should automatically incorporate the most recent update to Player won-lost records. In some cases, however, the accompanying text may have been written based on previous versions of Player won-lost records. I apologize if this results in non-sensical text in any cases.

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