Analyzing a pitcher can be one of the most interesting and time consuming exercises a baseball enthusiast can embark on. We have so much information today that it is hard to know where to begin. If you’re like me, you check the classic back of the baseball card stats, just as a quick primer, and then dig in from there.
Flip over Pittsburgh Pirates’ starting pitcher Jameson Taillon’s virtual card and his sparkling 2.86 ERA piques some interest, especially when compared to last year’s 4.44 ERA. So many variables and independent events go into that one number. We can’t really know anything about a pitcher based solely on ERA, but it’s a starting point. Let’s go from there to find out what has worked for Taillon so far this year.
What events lead to a pitcher’s runs allowed? So many things. Strikeouts, walks, batted ball luck, batted ball quality, sequencing of hits, reliever strand rate, official scorers, and more. There are so many layers to these events too. It’s overwhelming, but lets peel back some layers on Taillon.
Another is strikeout and walk rate, home run rate, batting average on balls in play (BABIP), and ground ball rate. His strikeout rate is a little up, while his walk rate is basically the same as it was last year. His home run rate is as good as it always has been. However, a .200 BABIP jumps off the page. That low total would have led baseball last year among qualified starters. You don’t have to look very far before you find a large contributing factor to this .200 BABIP. Taillon’s ground ball rate sticks out this year. It is up 10 percentage points up from the 2017 campaign, from 47 to 57 percent, which is currently fifth best in the majors. Now, where does that spike in ground ball rate come from?
More grounders
High ground ball rates most often come from guys with good command of a quality two seam fastball or sinker. It only takes a couple innings of watching Taillon to know that he possesses that trait. His best two seamers dart down and in on righties and down and away from lefties. It passes the eye test and the data backs it up too.
His two seam/sinker has a .236 wOBA against which is also fifth best in the majors and a .152 batting average against (min 20 FT, SI put in play). Taillon’s two seamer induces 68 percent ground balls which leads to poor results for the hitters. It makes perfect sense.
The only thing that does not make sense is why the results on that pitch are different this year. Last year, the wOBA allowed against his two seamer was .387, which is very far from fifth place in the majors. Taillon throws it with the same velocity and he gets about the same movement as he did last year, so the results of the pitch must be dependent on something other than the literal pitch itself. Another layer perhaps?
Pitch Mix
Pitch mix is a kind of puzzle that a pitcher puts together to figure out what combination of pitches they should throw and at what frequency to lead to their greatest possible success. There are not necessarily good metrics that tell us exactly what a pitcher’s best mix is, so we have to try to deduce what works best based on the other numbers that we have.
The results on Taillon’s two seamer changed. What else has? Well, the mix of Taillon’s two seam and four seam fastballs changed. This year, he is throwing his two seamer much less against lefties; down from throwing it 33 percent of the time to now throwing it 23 percent. The logic behind this change is pretty simple as a bad two seamer from a right handed pitcher can run back over the middle of the plate against lefties. Of course, concurrent to the decrease in two seamers to lefties is a 15 percentage point increase in four seam fastballs to lefties and a seven percentage point jump in two seamers to righties.
Below, you can see the reasoning for the change illustrated. The two seamer running away from a left handed hitter is a bad pitch, while the two seamer running in on the righties is a good pitch.
These are pretty significant changes, and despite it being early in the season, they are changes that I would imagine are deliberate and I would expect to remain throughout the season, especially given the success Taillon has had in the early going. I mean, a 2.86 ERA tells you all you need to know anyway, right?
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