Introduction

Today's baseball analysts pay rather close attention to flyball, line drive, and groundball rates of hitters and pitchers in order to gain a deeper understanding of the player's seasonal and/or projected performance. Just looking a player's rate of a general batted ball type can reveal something about their relative ability to avoid/create that variety of event, but doing so is a bit of a simplification in so much as the most typical consequences of those batted ball events can change rather dramatically based on the direction of the field to which they are hit and individual players often display characteristic directional biases on certain batted ball types.

Purpose

The objective here is to filter out batted ball events that occurred in American League parks and categorize them based on the general type of batted ball event, the directional zone of the field to which the ball was hit, and the plate appearance outcome.

Methods

The batted ball event data from every 2013 game played in an American League (AL) park through July 31 was downloaded from the MLBAM Gameday web archives and organized into spreadsheets. The text from the description fields of each play were searched to classify each batted ball event as either a groundball (GB), line drive (LD), outfield fly ball (OFFB), or infield fly ball (IFFB) and for each event the two coordinates of the field where the ball was fielded (or landed beyond the fence) was also recorded. The two foul lines of an MLB stadium form a 90-degree angle and as such one can resolve the fair portion of the playing field down to three 30-degree pie slices and for the sake of this analysis the leftmost one will be the Left-third of the field, the middle sector will be the Center-third of the field, and the right-most one will be the Right-third of the field. Using those coordinates each fair batted ball can be placed into one of the thirds, and for the sake of what follows all bunts and foul popups/flyouts have been excluded so the presented data will only include fair nonbunted balls. Each batter's batting handedness was further used to classify the Left- and Right-third of the field as their Pull-third and Oppo-third, or vice versa. The result of each play was also identified: single, double, triple, home run, or out (inclusive of reached base on error, reached base on fielder's choice attempt, and sacrifice fly events).

To keep the computations and analyses straightforward, only batting average (AVG = hits divided by plate appearances, in this study) and slugging percentage (SLG = total bases divided by plate appearances, in this study) will be reported for each permutation of batted ball event and field-third direction. This data was broken down further to compare lefthanded batters (LHB) to righthanded batters (RHB) across all American League parks and within the confines of MinuteMaid Park.

Results

AL Parks, Frequency of Batted Ball Event by Direction

The most common batted ball event by a comfortable margin is the Pull-third GB (LHB: 22%, RHB: 26%) with the adjacently-situated Center-third GB next (LHB: 15%, RHB: 14%). The big difference between LHB and RHB is that RHB more frequently pull their grounders; RHB hit 5 to the Pull-third for every 1 to the Oppo-third, whereas LHB hit 3 to the Pull-third for every 1 to the Oppo-third. RHB in MinuteMaid Park seem to especially favor pulling their grounders, perhaps in an ill-fated quest to visit the enticingly-close Crawford Boxes on a pitch that is difficult to pull in the air; whether this is a home/road/combined-team effect seems worthy of future examination.

All AL Parks, Batting Average of LHB vs RHB by Batted Ball Type and Direction

Once the data is pooled across all parks, the LHB and RHB numbers end up being very similar with the exceptions of LHB hitting for slightly lower average on groundballs to the Pull-third and Center-third, a result which likely stems from the more aggressive shifting of infield defenders to the right versus LHB (if not also a smidgen of shortening of the throw to first).

Based on the above data, if the situation called for any variety of hit the batter would hypothetically be best off from an AVG standpoint hitting a Pull-third LD (LHB: 0.709, RHB: 0.720) first, a Center-third LD (LHB: 0.678, RHB: 0.663) second, and an Oppo-third LD (LHB: 0.647, RHB: 0.655) next. And then there's a large drop in AVG down to the Pull-third OFFB (LHB: 0.458, RHB: 0.456), and then another big decline down to a bit of a surprising outcome in that Oppo-third GB (LHB: 0.336, RHB: 0.329), Center-third GB (LHB: 0.257, RHB: 0.282), and Pull-third GB (LHB: 0.189, RHB: 0.216) are each more likely to result in a hit than are Center-third OFFB (LHB: 0.185, RHB: 0.171) and Oppo-third OFFB (LHB: 0.161, RHB: 0.158). IFFB are not shown here and beyond as the AVG on these to any third of the field was a measly 0.036 and they pretty much never result in a extra-base hit. IFFB are rather clearly the worst batted ball outcome for a hitter and best for a pitcher conversely (when no runners are on base, at least) and that should not be forgotten.

All AL Parks, Slugging Percentage of LHB vs RHB by Batted Ball Type and Direction

If you can think of batting average as the number of hits per batted ball in the preceding section, you can consider slugging percentage as the number of total bases generated per batted ball.

Here, the Pull-third OFFB (LHB: 1.590, RHB: 1.572) jumps well to the top given the hefty percentage of home runs that fall into this category (56% of the homers in this sample were Pull-third OFFB, 17% were Center-third OFFB, 10% were Oppo-third OFFB); a Pull-third OFFB is essentially 1.1 to 1.2 total bases better than an OFFB hit elsewhere and equivalent in total bases to 3 to 4 of the latter events. While you may recall that the Center- and Oppo-third OFFB had lower batting averages than each variety of GB, you can see that in the Center-third an OFFB yields almost twice the total bases that a GB does (LHB: 0.476 vs 0.259, RHB: 0.434 vs 0.283) while in the Oppo-third the OFFB and GB yield an equivalent number of total bases (LHB: 0.360 vs 0.365, RHB: 0.376 vs 0.359).

Turning attention to LD, Center- and Oppo-third LD yield comparable SLG values in the neighborhood of 0.850 to 0.900 that are about 0.250 less than what Pull-third LD garner (13% of the homers in this sample were Pull-third LD vs 2% each for Center-third LD and Oppo-third LD; 31% of the doubles in this sample were Pull-third LD vs 16% for Center-third LD and 15% for Oppo-third LD). So a pulled line drive is generally a quarter of a total base better than one hit to other parts of the field.

MinuteMaid Park, Batting Average of LHB vs RHB by Batted Ball Type and Direction

At the individual park level unique characteristics of home team batters, pitchers, and fielders assume increased influence on the results as a group of those players participate in every game played in the park. There are a few mathematical tricks that can be used to neutralize the contributions of the home team's players to the results but for now I will simply report the data as is.

Looking at OFFB, RHB are not surprisingly out-hitting LHB on Pull-third OFFB given the close proximity of the Crawford Boxes and the tall fence in front of them; that 0.571 AVG is the 2nd highest of all 15 AL parks for the Pull-third OFFB with the other close-and-tall-LF-fenced stadium, Boston's Fenway Park, ranking 1st at 0.672 (the AL norm is 0.456, by comparison). The 0.229 mark by LHB on Oppo-third OFFB is also 2nd-highest in the AL so again the Crawford Boxes are boosting numbers in that direction (Fenway ranks 1st again by a large margin at 0.383). The LHB Pull-third OFFB 0.500 AVG ranks 6th among AL parks.

In terms of LD, while there was a gradual drop in AVG in AL parks in moving from the Pull-third across to the Oppo-third, in MinuteMaid Park LD are yielding similar results in the two corner zones; the LHB Oppo-third result is fairly easy to explain but not so much the RHB Oppo-third result.

Turning attention to GB, the peculiar result is what happens when RHB hit the Oppo-third GB; a whopping 35 of the relatively scarce 70 such events have produced a hit with the corresponding 0.500 AVG ranking 1st among AL parks and dwarfing the 0.329 AL norm for the event. Breaking that rather small sample down further shows that most of the hits have occurred with the Astros on defense (.537 AVG) though the offense's AVG is also elevated (0.448). The RHB Center-third GB 0.329 AVG (84 hits in 255 events) ranks 3rd highest among AL parks and well above the league 0.283 AVG norm, but in this case the hits occur at a nearly identical rate when the Astros are on defense and offense.

MinuteMaid Park, Slugging Average of LHB vs RHB by Batted Ball Type and Direction

MinuteMaid and Fenway flip places on the Left-third OFFB slugging stats leaderboard, as MinuteMaid claims the top spot for RHB Pull-third OFFB and LHB Oppo-third OFFB (theory: the switch with Fenway is due to fence height). That 2.095 slugging percentage on RHB Pull-third OFFB is well over the AL norm of 1.568 and re-emphasizes why you want the Astros RHB hitting flyballs to left there and relatedly do not want Astros pitchers surrendering the same event to RHB; stated differently, the equivalent outcome to a RHB flyball to left field in MinuteMaid is 2.095 total bases or essentially a double plus an 8.5-foot lead off second. The LHB Pull-third OFFB 1.859 mark is 3rd-highest in the AL and also points out that pulling OFFB is also a rather good thing for LHB in MinuteMaid (bad thing for pitchers).

Though the LHB Oppo-third OFFB 0.706 SLG is tops in the league that finding should not in itself scare pitchers off from pitching run-of-the-mill LHB away there given how small that number is relative to the 1.859 Pull-third value. The 0.350 mark on RHB Oppo-third OFFB looks tiny versus the LHB Oppo-third value, but in truth it's just a bit under the 0.379 AL norm for RHB.

Of the LD events, RHB Pull-third, RHB Oppo-third, and LHB Oppo-third rank 4th, 1st, and 1st in SLG for said LD event among AL parks.

Conclusions

In constructing the ideal hitter to deploy against a relatively standard MLB defensive alignment, you would engineer him to:

1. hit line drives to all fields with a slight bias towards the pull-third field where slugging is maximized (0.650 to 0.715 AVG, 0.870 to 1.100 SLG)
2. hit flyballs to the pull-field third of the outfield (0.460 AVG, 1.580 SLG) when the opportunity presents, and settle for hitting a fly ball to the center-field third (0.180 AVG, 0.450 SLG) or opposite-field third (0.160 AVG, 0.370 SLG) if the loftable pitch is difficult to pull and the park is one that rewards a fly ball hit that way with a higher than typical slugging result
3. hit pitches that are difficult to loft as groundballs to the opposite-field third (0.330 AVG, 0.360 SLG), or alternatively to the center-field third (0.270 AVG)

In constructing the ideal pitcher to deploy against MLB hitters, you would engineer him to throw pitches which when contacted by the batter generate mostly:

1. pull-field groundballs (0.200 AVG and 0.230 SLG)
2. opposite-field (0.160 AVG and 0.370 SLG) or center-field (0.180 AVG and 0.450 SLG) outfield flyballs
3. infield fly balls (0.040 AVG)

If MinuteMaid Park were the home stadium, then you would drill into the player:

1. how the park's architectural configuration amplifies the offensive outcomes of pulled flyballs (RHB: 0.570 AVG and 2.100 SLG, LHB: 0.500 AVG and 1.860 SLG)
2. that hitting flyballs to left-field is a good fallback plan there for LHB on loftable pitches that are difficult to pull (0.230 AVG and 0.710 SLG)

Future Directions

• To what extent is MinuteMaid Park skewing the MinuteMaid Park results?
• To what extent are the 2013 Astros skewing the MinuteMaid Park results?
• Which 2013 Astros pitchers and hitters are beating/trailing what their AVG and SLG on batted balls should be per their batted ball directional profiles? And which of them would seem to be better/worse fits for MinuteMaid Park based on the directional biases of their batted ball types?
• How well do the 2013 Astros prevent groundballs sent to each third from becoming hits, relative to league standards? And versus LHB in comparison to versus RHB, especially as it relates to infielder shifts?
• What about the third dimension of the batted ball trajectory - the launch angle off the bat relative to the ground - as surely some groundballs, line drives, and outfield flyballs hit to a given third of the field are better than others based on that value?