Foreword
Coaching baseball at a high level is not an easy task. Modern baseball requires coaches to understand a lot about data analysis, biomechanics, psychology and other scientific topics but it also helps to have a good playing experience to have credibility with the players and to be able to relate to their challenges and mental struggles.
In the last couple years that has lead to a lot of conflicts in baseball. On the one hand you have „old School“ Coaches who have a wealth of experience and can relate to players but are a bit inflexible when it comes to adopting new methods. Often those coaches will coach what they did themselves in training when they where young and feel threatened by modern methods and new coaches. This can lead to those coaches attacking and trying to push away „new school“ coaches who are entering their territory. Those structures can make changes in a baseball organization tough to achieve as front offices who bring in new coaches can get pushback by the established group of coaches.
This has caused some teams to hire new coaches from outside of pro ball with a strong academic background like biomechanics, data science or other fields. Those coaches are often more skilled in understanding nuances of modern training and player development and more open to bringing in change. However the downside is that sometimes it is not easy to get buy in from players when coaches didn’t play at their own level or higher.
Thus it is ideal if you have coaches who have the knowledge and flexiblity but also ideally good playing experience. The goal of this book is to bring players up to speed so they can contribute in the modern coaching environment.
Data Basics for hitting
Understanding data isn’t the most fun aspect for many player but baseball always has been a numbers oriented sport and this tendency only got more over the years. The goal of offense in baseball is to score runs. The more runs you score the higher your chance to win. Ever since the book „Moneyball“ it has been well known that avoiding outs and getting on base is very valuable. Whether you get on base via a hit, a hit by pitch or a walk, getting on base means that the inning continues and you can score more runs. In theory by getting on base consecutively you can score infinite runs which in turn means in theory you only need 9 guys who can get on base a lot and you will win. However in practice high level pitchers are very good and they will try to avoid giving up walks and hits. This means a second aspect of hitting becomes very important and that is power. Power allows you to score more runs with one swing. There is no clock in baseball but in practice against good pitchers your „time“ to score runs often is limited because how good they are at avoiding runners on base. To combat that it helps to have hitters who can score some runs with one swing before the third out is made. Ideally thus as a hitter you have a combination of power and on base skills as a hitter so that you are able to hit in runners on base but also turn over the lineup and score runs yourself. A common stat that captures both on base ability and power is OPS which adds up the on base percentage with the slugging percentage that measures power. There are also more refined stats like wOBA and wRC+ using more refined mathematical models than OPS but as a „quick and dirty“ method OPS is suprisingly good at capturing the quality of a hitter. An average hitter usually has an OPS around in the low 700s, bench players tend to be in the 600s and stars tend to be at 800+. Slugging percentage weighs the batting average by extra bases as singles are count by 1, doubles by 2 and so on. That means a player who just hits singles will have the same batting average and slugging percentage. If you subtract the batting average from the slugging percentage you get the so called isolated slugging (ISO). A league average ISO depending on the run environment is like around .150-170. Good sluggers are well over .200 and under .100 is really low.
Batting average itself is not a good measurement of production however since batting average usually makes up 50-60% of a players slugging percentage and about 70-80% of a hitters on base percentage the hit tool is still very important. That being said a pure empty batting average hitter usually is still not very productive (a .300/.300/.300 line still is a below average .600 OPS) but a good hit tool can take away pressure from the need to slug.
For example Luis Arraez as of 2024 has a solid .787 OPS despite a low .095 ISO and a low-ish 7% walk rate (League average is around 9%). Batting average makes up for 86% of Arraez OBP and 77% of his SLG.
On the other hand Joey Gallo who has a very low hit tool has a similar .780 career OPS despite a .195 career Batting average but with an elite walk rate (14.7%) and ISO (.263). His batting average only makes up for 60% of his OBP and 42% of his SLG.
However while this approaches can work it usually is good to have at least 2 out oft he big 3 hitting skills (power, batting eye, contact ability) because if one or two skills are really rock bottom the rest can’t afford to drop the slightest. For example Arraez even at a solid .280 batting average would be a below average player and Gallo is so low in one skill that he even needs two elite skills to even be playable. The „safest“ way for a hitter is to be competent in all 3 of the crucial skills.
Plate discipline data
As we talked about in the prior chapter contact ability and batting eye are very important skills. You don’t need to have elite plate discipline to be a good hitter but having a good plate discipline means there is less pressure on your batted ball quality. Hitters with bad strikeout to walk ratios need a very high batted ball quality, while good K to BB hitters can get away with a little less power.
The league average strikeout rate in the last years was around 22-23%, the average walk rate about 8-9%. Getting more granular there is also plate discipline on a pitch level base. Here o-swing%, i.e. pitch percentage out of the zone that is swung at is important. Generally having a lower o-swing% (also called chase rate) is better as pitches out of the zone create more swing and miss and less slugging. League average chase rate is around 30%, a good chase rate is around 25% while above 35% is very bad. So patience does help hitters, on the other hand it is also good to have a high in zone swing rate. Ideally it should be above 65% as a too passive approach can lead to falling behind in the count. The count of course is very important as the league is hitting well under .200 with two strikes so you don’t want to give away too many called strikes, but you also don’t want to get yourself out by chasing balls as overall the contact rate in the zone (around 85%) is well lower than outside the zone (just over 60%).
So generally of course you want to swing at strikes and take balls but early in the count you can also shrink your zone a little. Statcast does divide the zone not just in balls and strikes but also in different „attack zones“. More over the heart of the plate they call it heart, while around the edges they call it „shadow“ and beyond that chase and waste. In the heart of the zone hitters are batting over .300, in the „shadow“ around the edges just 220 and in the chase zone just .107. That means early in the count it can be beneficial to give the edges tot he pitcher and make him come more over the plate. Statisitically about 1 in 4 pitches are over the heart, so on average you will get about one such „mistake“ per plate appearance. Key is to not miss that pitch even when it is early in the count. So a good hitter shouldn’t chase outside the zone but also be very aggressive in the heart of the plate. Generally higher contact hitters can be more selective inside the zone, they can afford to give away a called strike because they still can make contact later in the at bat. On the other hand for higher swing and miss guys it can make sense the work on covering the whole zone with good batted ball quality. Ideally that guy still shouldn’t chase outside the zone but it still can make sense to reduce called strikes so you get a second swing with less than two strikes. On the other hand low powered high contact hitters should do everything to avoid making weak contact early in the count on the edges of the zone and instead maximize their batted ball quality by definitely making the first swing of the at bat on a pitch that is well over the plate.
Batted Ball data
The best batted ball event usually of course is a line drive which is common knowledge. Statcast defines line drives as batted balls hit between 10-25 degrees. The league is batting over .600 on line drives. Also line drives are rather insensitive to exit velocity, even softer liners often are hits. For example in 2022-2024 liners hit at under 90 MPH yielded a .604 batting average vs .651 above 90 mph.
On the other hand of course there are pop ups which statcast defines as fly balls hit at a higher than 50 degrees, those of course are almost always outs, not much better than a strikeout. So high pop up numbers are to be avoided.
Those two batted ball types are pretty staightforward but with fly balls and ground balls it is getting more complicated. Overall the batting average on ground balls has been .241 over that time frame vs .266 for fly balls. However fly balls are very exit velocity dependent. Hit under 100 MPH fly balls just yielded a .140 average, above 100 it was .669. Even more dramatic it shows in the slugging. Fly balls hit at 100+ MPH yield a huge 2400 SLG%, under 100 it is just .297. Ground balls on the other hand generally just yield a .266 SLG which isn’t much higher than the .241 average. That means as a hitter you either want line drives or hard hit fly balls, while pop ups, soft fly balls and most grounders should be avoided. Above 100 MPH grounders still yield a solid .400 batting average but the SLG is well short of the over 2000 on fly balls and over 1000 on line drives of the same exit velocity. Pulled liners perform a bit better but the difference is not huge.
The effect of batted ball direction also is interesting. On line drives the SLG on pulled balls is about 1000 vs .794 on center and oppo line drives. On the other hand on fly balls the slugging on fly balls hit the other way or up the middle is .477 and more than 3 times as high at 1700, so pulled lfy balls perform a lot better, because the field down the lines is shorter and pulled balls tend to be hit a little harder since the ball is hit more out front.
On ground balls it is the opposite, grounders up the middle and oppo yield a .284 batting average vs just .197 to pull side. That is the downside of a too pull heavy approach, you want the pulled fly balls but generally for most hitters pulling leads to more grounders because hit out front there is more risk of rolling over the ball.
Overall the league launch angle on pulled balls is around 6 degrees vs over 10 up the mdidle and over 20 the other way. This is why you can’t just every hitter to pull the ball more, some hitters who have big exit velos but struggle to pull it in the air might be better off with an up the middle gap to gap approach because high pull hitters who roll over a lot can hit for power but also have lower batting averages on balls in play. Most elite hitters tend to have pull rates of around 40-45%. Lower than that power will suffer unless the hitter has huge raw power, higher than that the batting average can suffer and also whiff rate and chase can go up because in order to pull you need to start the swing a little earlier giving less decision time.
However there are some factors that can help very high pull hitters (above 45%) to succeed. Players like Alex Bregman or Isaac Paredes don’t have great raw power but still can produce high power numbers with a pull heavy approach. Those hitters usually need to have better than average chase and whiff rates so they can start the swing earlier and still not whiff or chase a lot. They also need to be able to pull the right pitches, so they need to have a good plan and plate dicsipline inside the zone. For example it helps if you are a good high fastball hitter as pulled balls low in the zone just had a 2 degree average launch angle vs 14 degrees in the upper 3rd of the zone yielded a 14 degree launch angle. Generally higher pitches are easier to hit in the air but also can lead to higher whiff and pop up rates.
Generally it probably is a good thing to spend some time developing the ability to hit pulled balls in the air but it needs to be done sensibly as too much pulling can have negative side effects, especially on the wrong pitches (soft stuff low and/or away). A complete hitter should be able to hit pulled fly balls at 100+ MPH but also be able to hit a hard liner the other way, if you only hit weak slices the other way it is not good either because good pitchers might be able to exploit that.
Regarding launch angle most elite hitters tend to have an average launch angle of about 12-17 degrees, the top10 hitters of 2024 are averaging 14 degrees. You also want to avoid too high ground ball rates, most elite hitters tend to be at around 35-45% ground balls, too many ground balls will often lead to less power output but players with a too high average launch angle of above 20 degrees can struggle too. A great stat is the statcast launch angle sweet spot percentage which measures percentage of balls hit between 8 and 32 degrees, a really great value here is around 40% or more while values under 35% are not good.
To summarize a good goal line to achieve by a hitter is about a 15 degree average launch angle, 10% average launch angle to the pull side, 40% ground ball rate and 40-45% pull rate. Also ideally 40+% of balls are hit hard at 95+.
Mechanical Considerations
The baseball swing is a motion where the full body is used to accelerate the bat as much as possible in a time frame that is as short as possible. Elite MLB swings take about 150 milliseconds or less which is needed because the ball delivered by the pitcher takes less than half a second to the plate. To produce elite power good power hitters reach batspeeds at contact of 75 MPH and more. Also the direction and shape of the swing is important. The attack angle is how much the bat travels up or down. Blast motion is a bat sensor that isn’t very expensive and can measure this angle. According to blast motion the best mlb hitters have a slightly positive attack angle of +6-+15 degrees. A steeper attack angle makes it easier to lift the ball but a flatter attack angle of 5-10 degrees might lead to more contact as the bat is matching the plane of the pitch better.
https://blastconnect.com/training_center/item/209#gref
The vertical bat angle also is important. Blast can measure this angle too.
https://blastconnect.com/training_center/baseball/metrics/baseball-swing/50#gref
Vertical bat angle is depending on the pitch height, the higher the pitch, the flatter it should be. So on a high pitch VBA might be around 15-20 degrees and on a low pitch 45+. VBA shouldn’t be created by the bat but due to side bend with the upper body, the bat should be perpendicular to the spine.
https://x.com/dominikkeul/status/1516156342444118031
It can make sense to start players working on high tee drills on a more flat swing and then gradually add more side bend and VBA. VBA is especially important on low pitches because it allows to hit low balls in the air instead of rolling over.
There are theories and data that point to steeper average VBAs creating a higher batted ball quality (especially less pop ups) for a lot of players as getting under the ball with a steeper VBA leads to spraying the ball the other way rather than popping it up with a flatter bat so it can make sense to look into VBA but we need more data on that to get conclusive evidence which we likely will get when statcast introduces more granular bat tracking data.
Another important aspect is the kinetic chain. Ideally the swing should start with the lower body accelerating first while the hands and bat are lagging back and then accelerate forward as the lower body already decelerates. The swing will start with a load where the back leg is loaded and often the hips are coiling into that back leg and the hands or rear scapula pulling back and around to control the forward move and be able to launch off that back leg into the front leg which is firming up and „bracing“ so the energy is transferred ideally into the upper body.
There are tracking devices that can measure the movements through the kinetic chain and determine whether there are issues in the sequence. Driveline baseball has some good articles about Kvest which provides tracking that can be used outside of a high tech biomenchanics lab.
https://www.drivelinebaseball.com/2018/11/introduction-k-vest/?srsltid=AfmBOoqyGcHazch313VlqMvhyBBXbE5IgbJoEjDzp2UQnVBTo1tpfnGD
Bat tracking data on statcast
Blast motion can deliver bat tracking data like attack angle, VBA or swing time to impact but the use is only allowed in training and not in games. Fortunately statcast now has some bat tracking data. As of now they do not have advanced tracking like VBA and AA (I expect that in further iterations) but they do have batspeed, swing length in feet (contrary to the time measurement that blast provides). Higher batspeed generally means more power but a long swing can cause more swing and miss. Fort hat reason it might be ideal to generate a high batspeed with a shorter swing. The league averages measured by statcast in 2024 are about 72 MPH and 7.3 feet of swing length. There needs to be more reasearch but we can assume that a longer than average swing that is slower than average is not great. However if you have a slow and very compact swing you can still have good results when bat to ball ability is elite and chase rate not too bad. For example Arraez had the slowest but also the shortest swing in baseball in 2024.
https://www.mlb.com/news/what-you-need-to-know-about-statcast-bat-tracking
