**Component 8 vs. Component 9: The Relationship between Baserunner Outs and Baserunner Advancements**

For fielders (mostly outfielders), conventional wisdom suggests a similar negative relationship as the outfielders with the strongest arms will simply deter baserunners from trying to advance (Component 9), leading to relatively fewer baserunner outs (Component 8).

Looking at Components 8 and 9, how do players' Component 8 winning percentages compare with their Component 9 winning percentages? I calculated weighted correlations for Component 8 and 9 winning percentages across all of the years over which I estimated Player won-lost records (1921 - 2017). Correlations range in value from -100% to +100%. A correlation of +100% would mean that Component 8 and Component 9 winning percentages were perfectly proportional. A correlation of -100% would mean that Component 8 and 9 winning percentages moved in precisely opposite directions. A correlation of 0% would mean that Component 8 and 9 winning percentages are entirely unrelated.Basic Correlation between Component 8 and Component 9 Winning Percentages

The results are as follows:

**Batters**:
-3.09%

**Baserunners**:
-0.26%

**Fielders**:
1.05%

In general, all of these correlations are extremely small, suggesting - somewhat surprisingly, perhaps - that Component 8 and Component 9 are essentially uncorrelated, and are, therefore, likely measuring distinct skills

Alternately, this apparent lack of correlation could be the result of offsetting correlations.

On the one hand, good baserunners tend to be good at all aspects of baserunning, and it makes sense that outfielders with good throwing arms would be good at everything which involves throwing. This would suggest a strong **positive** correlation between Components 8 and 9.

On the other hand, the logic which I laid out above - (1) that fielders who have the best throwing arms deter base advancement and therefore have less opportunity to throw out baserunners, or (2) that aggressive baserunning may lead to higher-than-average Component 8 losses and Component 9 wins - would suggest a **negative** correlation between Components 8 and 9.

If, in fact, both hypotheses are true, perhaps that explains the apparent lack of correlation - the positive and negative factors essentially cancel one another out.

In order to determine how to divide responsibility for Components 8 and 9 between batters and baserunners, I constructed a series of persistence equations which modeled Component 8 winning percentage on even-numbered plays as a function of Component 8 winning percentage for odd-numbered plays (and ditto for Component 9).Relationship between Component 8 and Component 9 Winning Percentages

One way to test the relationship between Components 8 and 9 is to see whether Component 8 winning percentage can help to predict Component 9 winning percentage and vice versa. To test this relationship, I modified the persistence equations that I estimated earlier to include Component 9 winning percentage in the Component 8 persistence equations and to include Component 8 winning percentage in the Component 9 persistence equations. I did this for outfielders (by fielding position) and baserunners (by base). The results are summarized below.

The basic persistence equation used in my work is the following:

(Component Win Pct)_{Even} = b•(Component Win Pct)_{Odd} + (1-b)•(WinPct)_{Baseline}

c•(Component 9 Win Pct)_{Odd} for the Component 8 equation, and

c•(Component 8 Win Pct)_{Odd} for the Component 9 equation

The numbers in parentheses are t-statistics. T-statistics measure the significance of b and c, that is, the confidence we have that b and/or c are greater than zero. The general rule of thumb used by most statisticians is that if a t-statistic is greater than 2, then we can be at least 95% certain that the true value of the underlying variable is greater than zero (given 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.

Persistence of Components 8 and 9 Winning Percentage: Left Fielder

Component 8: WinPct8_{Even}= (30.03%)•WinPct8_{Odd}+ (69.97%)•0.5000 + (3.72%)•WinPct9_{Odd}(32.78) (2.686)

Component 9: WinPct9_{Even}= (11.98%)•WinPct9_{Odd}+ (88.02%)•0.5000 + (1.47%)•WinPct8_{Odd}(12.92) (2.974)

Component 9 winning percentage shows up as a somewhat significant factor in helping to predict Component 8 winning percentage. The reverse, however, is not true.

Persistence of Components 8 and 9 Winning Percentage: Center Fielder

Component 8: WinPct8_{Even}= (42.77%)•WinPct8_{Odd}+ (57.23%)•0.5000 + (12.99%)•WinPct9_{Odd}(42.57) (7.690)

Component 9: WinPct9_{Even}= (17.64%)•WinPct9_{Odd}+ (82.36%)•0.5000 + (-0.58%)•WinPct8_{Odd}(15.82) (-1.048)

Although both of the relevant t-statistics here are significant, they are of opposite signs, which doesn't really seem to make sense.

Persistence of Components 8 and 9 Winning Percentage: Right Fielder

Component 8: WinPct8_{Even}= (25.19%)•WinPct8_{Odd}+ (74.81%)•0.5000 + (19.28%)•WinPct9_{Odd}(26.15) (13.23)

Component 9: WinPct9_{Even}= (9.59%)•WinPct9_{Odd}+ (90.41%)•0.5000 + (1.68%)•WinPct8_{Odd}(9.365) (3.138)

As with left fielders, Component 9 winning percentage shows up as a significant factor in helping to predict Component 8 winning percentage, but the reverse coefficient is not significant.

Persistence of Components 8 and 9 Winning Percentage: Baserunner on First Base

Component 8: WinPct8_{Even}= (42.47%)•WinPct8_{Odd}+ (57.53%)•0.5000 + (-5.47%)•WinPct9_{Odd}(106.6) (-8.581)

Component 9: WinPct9_{Even}= (39.73%)•WinPct9_{Odd}+ (60.27%)•0.5000 + (3.70%)•WinPct8_{Odd}(96.65) (18.48)

Component 8 and Component 9 winning percentages both appear to have significant predictive power in explaining each other. Curiously, however, that predictive relationship is (significantly) negative in the Component 8 equation but (significantly) positive in the Component 9 equation.

Persistence of Components 8 and 9 Winning Percentage: Baserunner on Second Base

Component 8: WinPct8_{Even}= (40.27%)•WinPct8_{Odd}+ (59.73%)•0.5000 + (-10.00%)•WinPct9_{Odd}(93.47) (-12.65)

Component 9: WinPct9_{Even}= (18.09%)•WinPct9_{Odd}+ (81.91%)•0.5000 + (1.17%)•WinPct8_{Odd}(37.73) (7.174)

The results for baserunners on second base are broadly similar to the results for runners on first base, except that both coefficients here are somewhat smaller both in magnitude as well as significance.

Persistence of Components 8 and 9 Winning Percentage: Baserunner on Third Base

Component 8: WinPct8_{Even}= (77.56%)•WinPct8_{Odd}+ (22.44%)•0.5000 + (6.36%)•WinPct9_{Odd}(234.8) (13.96)

Component 9: WinPct9_{Even}= (-5.71%)•WinPct9_{Odd}+ (105.71%)•0.5000 + (1.80%)•WinPct8_{Odd}(-9.706) (6.641)

The results for baserunners on third base basically mirror those for baserunners on first and second base.

Based on these results, it appears to me that Components 8 and 9 are related, but nevertheless clearly distinct, skills for both baserunners and fielders.

*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.*

Based on these results, it appears to me that Components 8 and 9 are related, but nevertheless clearly distinct, skills for both baserunners and fielders.