Infield Defense Changes with Three True Outcomes

The point wasn’t to make Andrelton Simmons’ defensive performance in 2013 seem even more impressive.

It ended up that way, but the idea was actually to show that infield defense has become less important over time. Let’s back up and examine the idea: three true outcomes have increased dramatically throughout baseball history thanks to the proliferation of strikeouts and a steady increase in home runs.

Of course, the inverse would then be true for balls in play—a plate appearance either ends in one of the three true outcomes (walk, strikeout or home run), or it ends with a ball in play. If three true outcomes are on the rise, balls in play must be on the decline.

First, let’s make sure the data bears this out. The graphs below show the home run, walk and strikeout rates throughout baseball history and then the summed three true outcomes and, inversely, the proportion of balls in play.

If it’s not entirely clear from the graph, 2013 came just shy of the record for the largest proportion of plate appearances ending in one of the three true outcomes at 30.32 percent, bested only by 2012’s 30.48 percent mark. While walks were down slightly to 7.9 percent (well below their 1949 high of 10.4 percent) and home runs were down to 2.52 percent (from 2000’s high of 2.99 percent), strikeouts reached an all-time high at 19.9 percent.

In all, these changes resulted in the second-smallest rate of balls in play ever, edging below 70 percent for just the second time.

The logic here should be easy to follow—fewer balls in play means fewer chances for fielders, decreasing the relative importance of defense compared to pitching and hitting.

Even if only the “modern” era of statistical tracking is examined, balls in plays are down from 72.3 percent in 2003 to 69.7 percent in 2013, a 3.7 percent decrease. The batted ball mix hasn’t shifted much in that time either, though we did see fewer outfield fly balls the past two seasons.

What this shows, essentially, is that since 2003, the drop in balls in play appears to have impacted all fielders equally.

Unfortunately, data before 2003 is unavailable, but the stark drop in balls in play over time should make it clear that defense has become relatively less important—perhaps ground balls and hits on the infield were less prominent and this is just a shift back in the aggregate, but the increased rate of extra-base hits would lead us to believe the contrary, that infield defense was even more important in the last millennium.

In addition to fewer balls in play, though, teams have also moved to shift far more often. As Jeff Zimmerman outlined in The Hardball Times Baseball Annual 2014, shifting is in vogue. It makes sense, after all, since between 57 and 60 percent of pulled balls result in ground balls compared to 40 to 43 percent on balls hit to center and 22 to 27 percent on balls taken the opposite way. With advanced scouting and more data available, teams can better identify hitter tendencies and adjust with less risk. The fact that 24 hitters pulled at least 200 balls in play this year makes it even easier to do for the high-pull hitters (as Zimmerman notes, the top-20 players hitting into a shift accounted for over 2,500 plays in 2013, dropping their collective BABIP by 37 points in those situations).

Here are the number of each different type of infield shift last season, taken from The Annual:

2013 MLB Infield Shifts
Shift Type	Total Shifts
Three infielders on one side	2,620
Middle infielder over bag	3,675
Third base to right	125
Other	110
Infield up	891
Total IF shifts	7,421

That’s more than 7,000 additional plays that decrease the relative importance of each infield defender. While that statement maybe doesn’t hold for each individual shift, a heavy-shift approach requires less range and decision making from fielders. Because it’s unclear which fielder made a play on each shift, they can’t be subtracted from the whole below, but the increased reliance on shifts furthers the argument that defense has become somewhat less important.

To dig down further, we took a look at infielders using some of the more advanced fielding tracking data we have available. Specifically, we looked at balls in zone by position and total plays made by position to see how the role of each position has changed. The shifts aren’t excluded, but note that “balls in zone with traditional infield” would be 7,421 less and “normal plays” would be significantly lower, too.

Balls In Zone and Total Plays Made By Infield Postion, 2003-2013
	First Base		Second Base		Shortstop		Third Base		Infield
Season	BIZ	Plays	BIZ	Plays	BIZ	Plays	BIZ	Plays	BIZ	Plays	Plays/PA
2003	6099	4484	11739	10356	10434	9203	10741	7413	32914	31456	16.78%
2004	5406	4070	12129	9863	11995	9872	9007	6215	33131	30020	15.92%
2005	5493	4343	12825	10403	12821	10484	9271	6813	34917	32043	17.20%
2006	6366	4799	12679	10401	13218	10809	10880	7686	36777	33695	17.92%
2007	6697	4965	12192	10120	13019	10625	10623	7221	35834	32931	17.46%
2008	6568	4860	12805	10525	12753	10567	10623	7403	36181	33355	17.78%
2009	6097	4766	12482	10149	13075	10476	9747	6943	35304	32334	17.28%
2010	6025	4602	12641	10380	12959	10354	10157	7220	35757	32556	17.55%
2011	6675	5299	12709	10394	12286	10087	10404	7366	35399	33146	17.89%
2012	6508	5166	12619	10181	12274	9850	10079	7238	34972	32435	17.61%
2013	6622	5312	12548	10049	12256	9843	9919	7197	34723	32401	17.53%

What’s interesting, though, is that while the number of plays infielders have made has varied, it’s been largely consistent over the past decade-plus. The percentage of plate appearances that result in an infielder making a play has actually gone up by three quarters of a percentage point.

Let’s take a closer look position by position.

First Base

Key Statistics, First Base, 2003-2013
Season	Plays	BIZ	RZR	wRC+	Off	Def	WAR
2003	6099	4484	0.735	112	338.1	-488.5	76.4
2004	5406	4070	0.753	109	250.3	-454.0	67.0
2005	5493	4343	0.791	112	338.6	-463.4	75.3
2006	6366	4799	0.754	113	345.9	-424.2	76.5
2007	6697	4965	0.741	111	248.1	-430.8	65.9
2008	6568	4860	0.740	110	222.7	-465.6	66.4
2009	6097	4766	0.782	115	388.7	-435.8	81.6
2010	6025	4602	0.764	112	280.9	-420.6	70.2
2011	6675	5299	0.794	112	268.6	-456.3	70.4
2012	6508	5166	0.794	107	118.8	-517.3	51.8
2013	6622	5312	0.802	110	195.6	-507.8	53.5

First basemen have actually seen their defensive workloads increase over the past decade, largely a result of the fielders simply making more plays on the balls hit their way. Perhaps this is due to teams moving their first basemen around more aggressively to cover greater ground, a greater reliance on pull-hitting pushing more balls to the corners, or simply a move to more athletic fielders. The net result hasn’t actually been better defense in the aggregate. Instead, first base remains a position played with an offensive premium and one that has seen a precipitous drop in overall value the past several seasons.

Second Base

Key Statistics, Second Base, 2003-2013
Season	Plays	BIZ	RZR	wRC+	Off	Def	WAR
2003	11739	10356	0.882	88	-344.3	52.4	57.2
2004	12129	9863	0.813	89	-329.7	76.1	63.1
2005	12825	10403	0.811	95	-113.8	128.6	86.6
2006	12679	10401	0.820	90	-311.2	-9.3	53.0
2007	12192	10120	0.830	94	-126.2	83.5	81.6
2008	12805	10525	0.822	95	-106.3	90.8	87.0
2009	12482	10149	0.813	95	-116.8	101.3	87.6
2010	12641	10380	0.821	94	-169.4	86.7	79.7
2011	12709	10394	0.818	91	-218.1	102.6	78.1
2012	12619	10181	0.807	88	-306.9	93.3	64.9
2013	12548	10049	0.801	91	-237.7	30.6	63.1

The second base renaissance appears to be at an end. From 2005 to 2010, the position became nearly a league-average offensive position, essentially becoming a duplicate of third base for a short time. Over the past few years, however, second basemen are making fewer plays on a similar number of balls while the position has reverted to an offensive weak spot. The result, like with first base, is a precipitous drop in the overall value of second basemen on both sides of the equation.

Third Base

Key Statistics, Third Base, 2003-2013
Season	Plays	BIZ	RZR	wRC+	Off	Def	WAR
2003	10741	7413	0.69	90	-364.7	77.8	61.2
2004	9007	6215	0.69	99	-52.5	31.4	87.3
2005	9271	6813	0.735	98	-103.2	28.4	82.4
2006	10880	7686	0.706	102	75.5	58.9	96.5
2007	10623	7221	0.68	99	-45.8	29.9	82.9
2008	10623	7403	0.697	100	-45.8	48.5	90.4
2009	9747	6943	0.712	98	-69.5	53.2	91.6
2010	10157	7220	0.711	97	-110.6	45.1	76.7
2011	10404	7366	0.708	92	-267.9	-29.2	60.8
2012	10079	7238	0.718	100	-27.5	52.6	90.6
2013	9919	7197	0.726	97	-148.3	48.3	76.1

Either the hot corner wreaks havoc on the statistics available or it’s quite a fickle position. The returns have fluctuated wildly at third base over the past decade, with offense at times nearing league average and defense swinging from incredibly valuable to a net-negative. The result, as you might expect, is an up-and-down overall value.

Shortstop

Key Statistics, Shortstop, 2003-2013
Season	Plays	BIZ	RZR	wRC+	Off	Def	WAR
2003	10434	9203	0.882	85	-386.5	214.2	61.3
2004	11995	9872	0.823	86	-335.7	233.5	66.2
2005	12821	10484	0.818	88	-284.1	216.9	75.1
2006	13218	10809	0.818	86	-375.2	224.6	63.4
2007	13019	10625	0.816	90	-247.8	224.6	76.9
2008	12753	10567	0.829	88	-321.9	240.3	72.2
2009	13075	10476	0.801	87	-357.5	220.3	69.7
2010	12959	10354	0.799	83	-418.4	253.7	64.6
2011	12286	10087	0.821	88	-297.2	213.2	73.7
2012	12274	9850	0.803	86	-322.8	252.4	72.9
2013	12256	9843	0.803	85	-324.4	209.6	64.1

As expected, shortstop is the most important defensive position in the infield. We saw earlier how shortstops have been edged by second basemen in terms of overall number of plays but the degree of difficulty is far greater at short. As a result, even with the worst offense of any infield position, shortstop has been the second most valuable position in terms of total wins added. Note, however, that the total defensive impact of shortstops was down in 2013, as it had the lowest mark in the sample.

The lede mentioned that Andrelton Simmons’ 2013 season would now look even more impressive, and it should — not only did he post the fourth-highest defensive runs total since 2003 and the second best at shortstop, he accounted for 31.6 of the position’s total 209.6 defensive runs, more than 15 percent. Manny Machado’s season looks even more incredible at third, too, as his 33.6 defensive runs represent nearly 70 percent of the position’s total. Given that some positions have negative defensive value, there are surely countless examples of players earning infinite portions of a position’s defensive value, but the point is that Simmons and Machado had outstanding defensive seasons at a time when their positions appear to be providing less overall value than in the recent past.

While balls in play are down overall, infielders haven’t noticed an appreciable change in their workload the last decade.

The data doesn’t capture two key points: that prior to 2003, infield defense was likely even more important, and that while the numbers are steady, the increasing use of shifts likely makes some of the plays infielders do make easier. I’ll admit this runs counter to what I was expecting to find when I began researching the impact of three true outcomes on infielder defense. Obviously, then, the amount of plays made by outfielders is decreasing, a topic worthy of study for a future piece.