Is Kevin Siegrist evolving approach?

Kevin Siegrist has not allowed a run in a game since surrendering two back on April 20th against the Milwaukee Brewers, 11 appearances ago. Among these 10 scoreless appearances, the last four have been what are considered “clean” innings, meaning he didn’t give up a hit nor issue a walk. Further, Siegrist has struck out 50% (six of 12) of the batters he has faced over these four appearances. Already, this provides for a much more positive mood than my “For Kevin Siegrist, it’s not just a velocity problem” post from three weeks ago. And considering Brett Cecil’s continued struggles with his curveball, Siegrist’s performance becomes even more important to the National League Central-leading St. Louis Cardinals.

Let’s begin by taking a look at Siegrist’s pitch usage over the first two months (well, a month and a half, really) of the 2017 season:

As you can see in the table, thus far in May, Siegrist has essentially flip-flopped his primary offspeed option, while also increasing his usage of his fourseamer — which has remained steady from a velocity standpoint. In a vacuum, what does switching his primary offspeed option really mean? Not much at all, but when you take a closer look at the specifics (PitchF/x and Statcast data) of the pitch, keeping in mind that he’s publicly reported making overall mechanical adjustments, you begin to understand and appreciate the change:

In May, Siegrist has generated a higher spin rate on the curveball. Subsequently, knowing that higher spin on curves means more vertical drop, he, too, has experienced more downward movement on the pitch. What’s especially interesting is the sharp increase in horizontal (glove-side) movement as well, which I believe can be, at the very least, partly attributed to a lower release point on the pitch. Bottom line, the curve he is currently throwing in May is oh so very different from the one he was throwing in April. And it shows, as he generated exactly zero swings and misses on the pitch during the month of April, as compared to a whiffs per swing rate of 40% thus far in May.

A big reason behind this success is Siegrist’s ability to locate the pitch in an area that is more tempting to opposing hitters — meaning if they don’t swing, there is a good chance it will be called a strike. Well, remembering back to my Siegrist post from three weeks ago, the core location for each one of his pitches fell outside of the strike zone. Whether this was due to the inability to command his pitches or his purposeful nibbling around the zone due to diminished stuff, I don’t know, but it remained an undeniable fact. Thus far in May, the core location of Siegrist’s curveball is almost perfect, and guess what, it falls inside the strike zone:

Of course, Siegrist’s recent string of success could all be chalked up to reliever volatility, combined with an extremely small sample size, but keeping in mind the way the Cardinals are playing right now, I figured a positive pitch-related post was in order. I am cautiously optimistic about Siegrist and hope to eventually see that uptick in fourseamer velocity he keeps talking about. Fortunately, even if we don’t, it appears he has developed an offspeed pitch that is less reliant on his fourseamer for success.

As always, credit to BrooksBaseball.net and BaseballSavant.com for data used in this post.