Fortunately Statcast now has a function that allows to sort for batted ball direction. This opens the chance for some new studies. Until now we just had launch angle (LA) and exit velocity (EV), however, that is not quite perfect because we already new that it is easier to pull fly balls for power. This was known intuitively for a long time https://www.fangraphs.com/fantasy/getting-to-know-fly-ball-pull-percentage-fb-pull/ but was hard to quantify until now.
One of the effects is certainly that parks are bigger in center field than they are down either line. However I also looked at EV and average distance of balls pulled, hit to center and oppo at angles of 20-35 degrees which are typical HR angles. For this article I only looked at right handed hitters, -45 to -15 was defined as pull, -15 to 15 as center center and 15 to 45 degrees as oppo.
You can see that pulled balls yield a 343 ft distance and 92.4 EV. To center it is slightly lower (91.4/338) but to opposite field it drops dramatically to 290/86.2. From a physics standpoint that makes sense because the contact on inside pitches is supposed to be further out front so that the swing is slightly longer and thus has more time to accelerate to contact which probably means more bat-speed at impact.
wOBA supports this, while liners are relatively stable in production, the wOBA of pulled fly balls is dramatically higher. On grounders this trend is reversed and oppo grounders are better than pulled grounders.
I also looked at the top and bottom 20 of the league in pull and oppo LA:
You can see that pull LA has a pronounced positive effect while oppo LA even has a slightly negative effect. It might make sense to try to lift more on pulled balls and slightly try to suppress LA (“get on top”) on oppo hit balls. Not sure if this is possible with the same swing though, I think usually the guys having a high FB pull rate also have high grounder pull rates because that is the natural tendency of the swing.
So it seems to be pretty simple: pull the ball in the air and be productive.
However it isn’t quite as simple. Already before Statcast it was known that pulled balls are hit on the ground at a much higher frequency https://www.fangraphs.com/blogs/the-pros-and-cons-of-pulling-the-baseball-2/.
Launch angle supports that, pulled balls last year had an average LA of 5.6 degrees vs 13.1 for balls up the middle and 20 degrees oppo.
This makes sense and actually is something that isn’t easily combatted with the modern swing. The modern swing goes slightly up and pulled balls are hit out front. You can lift a ball like this but if you are a little too far out front the bat has risen above the plane of the pitch which means you hit the top of the ball and roll over hitting a hard topspin grounder, often into the shift.
This is especially pronounced on low pitches.
There are some hitters who have developed a tool to combat that rolling over with the uppercut swing as I have shown in this article https://www.fangraphs.com/community/finding-keys-to-elevate-the-ball-more/ by using a steeper bat angle but it is not easy to do as the league still tends to have much lower launch angles on low and especially away pitches https://www.fangraphs.com/community/effect-of-pitch-selection-on-launch-angle-and-exit-velocity/.
I broke this down a little more looking at batted ball directions and pitch locations inside the zone
You can see that low pitches that are pulled are especially hard to lift, most extreme is that on low and away pitches but even the down and in pitch only yields a modest 6 degree LA.
I also looked at pulled balls above 10 degrees on low pitches. The leaders in that stat were in this order Stanton, Machado, Salvador Perez, Hunter Renfroe, Nelson Cruz and Mookie Betts. Those were some pretty good hitters last year, so maybe that is a skill that deserves further examination.
We all have seen Bryce Harper pull outside pitches for a homer and it does happen but generally trying to pull anything away is not a good receipt. If it works it usually is on pitches up (still yields a positive 7 degree LA to pull up and away pitches).
An adjustment that might make sense is trying to hit up and away and middle away balls to center rather than the other way. That way you could bring down the average EV of those pitches from a too-high-upper-20s average EV to a better low 20s EV, which yields a better BABIP on those pitches which tend to yield lower EVs. I elaborated in this article why mid-20s LAs are ideal but actually average LAs should be lower (between like 12 and 18 or so)
Overall an LA optimizing strategy using batted ball direction could look like this.
So pulling the ball is good but only if you have the skill to put it in the air. Selecting the right pitches to do it certainly helps. On pitches that are low and away it still makes sense to follow the old advice to hit it were it is pitched. And for pitchers it might make sense to work the outside corner more, however that is also a fine line since you need to prevent the old Jose Bautista strategy of creeping closer to the plate and turning the outside pitch into a middle pitch. For this you need to pitch inside some to keep the hitters honest.