Josh Hader is incredibly hard to hit for several reasons. The biggest has to be because of his mechanics as Hader hides the ball really well (especially to left-handed hitters). He does so by angling his body towards the first baseline as you can see by his front foot position. The hitter is kept in suspense much longer than the average delivery. That’s important because when dealing with timing, we are talking about fractions of a second. Hader tends to make that timeframe as small as possible.
Not only that, the amount of movement Hader generates on his fastball is elite-level and a direct result of his near 100% spin efficiency.
An example of this declarations is Hader blowing away Javy Baez, one of the better hitters in baseball, with four fastballs last night in the ninth inning. The sequence is as follows: 95.8 (foul)-96.4 (ball)-95.8 (whiff)-97.9 (whiff).
As you can see from the plot chart above, Hader went middle in followed by three straight shots up and away from Baez. You would think seeing nothing but fastballs with similar velocities and zone plots, that a hitter of Baez’s caliber would catch up. Baez also has to remember that Hader has a pretty strong slider that can pair well with his fastball. Knowing you already have to calibrate your timing for his fastball, the slider can throw a wrench into your adjustment.
Hader loves to attack high in the zone with his fastball. With his slider breaking off that trajectory and coming in at roughly 14 MPH slower, he can be very hard to clock.
Baez didn’t see a slider during this plate appearance but he probably assumed he’d get one; or hoping, as his wOBA against sliders is 20 points higher than the league average.
Either Hader was mindful of this, or he just didn’t care. Here’s the last pitch of the at-bat.
Baez was something close to 10 MPH behind that pitch. Knowing that he’d have to account for the slider, its possible that Baez’s minds-eye was trying to split the difference (see: Perry Husband and Effective Velocity). In any case, below you will see the point at which Baez should have made contact if he wanted to connect with the highest-possible exit velocity.
Notice how late Baez was. Had the pitch come in maybe 8-10 MPH slower, he’d have made solid contact. The preceding image shows where that spot should have been.
By that time, the ball had already reached the catcher’s mitt and Baez was K’d.
Hader isn’t impossible to hit but he makes it really hard with his four-seamer alone. Travis Sawchik from The Athletic recently did a terrific rundown of the pitch and gave a hitter’s perspective on what happens as they face the rocket-armed southpaw. What’s more, Hader has the highest probability of drawing strikes two and three and also holds the lowest wOBA on hitters with two strikes.
Good luck, hitters.