Everyone is looking for keys to get players to elevate the ball. One important point is certainly the so called attack angle. The attack angle is the angle of which the bat attacks the ball (uppercut, level or down). Baseball used to teach swinging down but now you actually want a small uppercut. Players use different cues to achieve that. Common cues are for example leaning slightly back to the catcher and work up with the front elbow.
Up in the zone elevating is pretty easy. The league average launch angle (LA) in the upper third of the zone is 20 degrees. Even Christian Yelich averages 15 degrees in the upper part oft the zone. In a prior analysis I also found out that LA in the upper part of the zone has little influence on wOBA, the 20 lowest average LA guys in the upper third actually had a slightly better wOBA than the 20 highest LA guys (.402 vs .393). 170 out of 182 hitters last year averaged 10-plus degrees.
That is very different low in the zone. The league average LA in the lower third was just 5 degrees and over 30 guys actually had a negative LA. Here the wOBA for the high LA guys is 80 points higher than the low LA guys. The difference is made low in the zone.
So the key for the low LA guys is definitely still to lift the low pitch. So how can this be achieved? You definitely need to swing up and you also need to avoid rolling over and hitting a grounder to pull field which is what the sinker-ballers try to achieve.
One theory is that on low pitches you tilt the shoulders more down and hit with the bat pointing more to the ground. The cue is that for high pitches the bat turns more like a merry go round and on low pitches more like a ferris wheel.
— dominikk85 (@dominikkeul) October 23, 2016
This Ferris Wheel like path makes sure that the bat comes through more straight through from below rather than going across the ball which leads to rolling over.
Mike Trout is so good at this that he is able to sometimes even hit down and in pitches to dead center for a bomb while most have to pull that ball. Jeff wrote a nice article about this: https://www.fangraphs.com/blogs/jabo-mike-trout-has-a-new-trick/
Of course this Ferris Wheel path also has his disadvantages, for example Trout used to be very bad on high pitches the first 4 years of his career. Still he got away with that because most pitchers would only pitch up like once per at bat and not live up in the zone so Trout would just take but ideally a batter would flatten out the bat up in the zone and swing steeper down which Trout actually did last year causing him to improve up.
But the traditional level bat, level shoulders cue is definitely hurting on low pitches and made the sinker so popular. Now that more guys learn the new swing path the sinker doesn’t work as well anymore but there are still hitters who struggle down (like Hosmer and Yelich).
The pitch up is getting more popular but it can not suppress launch angle. The high pitch lifts itself, when a pitcher pitches up he needs to compensate for the higher LA by more pop ups, lower EV and more Ks.
It is a good sign that Hosmer now thinks about swinging up more but if he wants to increase his LA he either needs to stop swinging at pitches in the lower third and target pitches up or change the rotation axis of his bat to more vertical on top of his attack angle because if you swing up but across the ball on low pitches all you do is hitting your grounders with more topspin.
I measured the vertical angle of some good and bad low ball hitters. On the left of the picture you have Yelich and Hosmer and the other pics are Ortiz, Trout and Votto who are all excellent low ball hitters. All pitches I chose were about knee high and on the inside of the plate because that affects the bat angle.
What you can see is that Hosmer and Yelich have an angle in the mid 20s while the other three are in the low to mid 40s.
That is important because on low pitches the flat barrel will naturally rotate to the left causing top spin similar to a tennis top spin while the steep barrel will rotate up and on the line to CF. https://www.youtube.com/watch?v=MJHTQncT-AA
So to learn to elevate getting a positive attack angle by leaning slightly back and keeping the head over the rear hip during the turn and working the front elbow slightly up definitely is important, but you also need to match the rotation axis of the bat around its long axis with the height of the pitch. The old cue of not dropping the back shoulder and hit with a level bat has its merits on pitches above the waist where a too steep bat angle is indeed bad (see young Trout) but on pitches mid-thigh to knee height this cue is very destructive. In the upper third of the zone the bat angle will be relatively flat ,but in the lower third you need to drop the back shoulder and tilt the rotation axis oft he bat down to around 40-45 degrees.
That means changing the swing isn’t that easy, you have to account for several things. It can be done but it is some work, will we see Hosmer and Yelich making all those adjustments? If they don’t make it they could also adjust less and try to just avoid hitting the low pitch but of course, that would eventually give the pitchers an opening to exploit.
So far there is no improvement for Hosmer. It is early but his GB rate is 58%. He either needs to stay away from the low pitches and target pitches up (and away in his case) or make more changes to his swing.