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Spin Rates Don’t Matter for Sinkers

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At least, maybe not as much as how that spin is applied.

St Louis Cardinals v San Francisco Giants Photo by Thearon W. Henderson/Getty Images

It’s been a bit since I’ve continued the spin rate series and part of the reason for that is that the next couple of pitches I planned on looking at didn’t have clear connections between their spin rates and the quality of the pitch, at least going by what we can see on Baseball Savant. One of those pitches was today’s topic: the sinker.

In today’s era of high-octane fastballs, the sinker is becoming a pitch that’s seen less often. However, pitchers who can effectively pitch to contact using sinkers have a couple of advantages over pitchers who rely on swing-and-miss stuff. First, sinker-ballers can typically work a lot more efficiently than their strikeout-heavy counterparts. Forcing groundballs early in counts is going to keep pitch counts down, while strikeout pitchers will need more pitches per batter, often leading to less efficient outings (this inefficiency is my one complaint about Jack Flaherty’s performances so far). Admittedly, there are times when pitching to contact can go terribly wrong. There isn’t much of a Plan B when opposing hitters are seeing and hitting pitches well, and the results for sinker-reliant pitchers are often only as good as the defense behind them.

The other advantage is that the increased tendency to produce groundballs is typically going to limit the damage done by an opposing offense. The authors of The Book analyzed the matchups of players based on flyball/groundball tendencies. Pitchers who tend to force groundballs perform better against both groundball and flyball hitters compared to pitchers that tend to force flyballs. So while there are weaknesses in being too reliant on the sinker, there is still quite a bit of incentive to add it into a repertoire.

But what makes for a good sinker? We’ll look at spin rates, but the focus of this piece is going to broaden a bit compared to my other pieces on spin rates. We’ll be looking at other aspects of pitch design to demonstrate what good sinkerballers might be doing to get their results. To start, I used the same process as before to select for a smaller range of velocities:

The majority of sinkers fall between 92 and 94 MPH, so we’ll be looking at pitchers from 2016 to 2021 with sinkers within that range. Next, we’ll compare the spin rates of these pitchers to their whiff rates when they throw sinkers, since that’s where we saw the best trend for four-seamers in the last piece. I’ve also labeled points representing Steven Matz, Dakota Hudson, Miles Mikolas, and Lance Lynn so we can see where they fall in the following graphs.

Contrary to what we saw for four-seamers, the spin rates of sinkers seem to have no bearing on whiff rates, but maybe there’s another metric that can provide insight. We’ve seen previously in the four-seamer analysis that spin rates don’t correlate with stats that track production on balls in play (such as wOBA and slugging percentage), so we’ll leave those comparisons on the shelf for this piece. But what about something more general, like launch angle? Sinkers that are more effective should produce more ground balls, making for an average launch angle closer to or below zero degrees (parallel to the ground).

Again, we find no relationship between spin rates and balls in play. Not expecting to find much, I ran the same analysis to compare spin rates with opponent BABIP (which is heavily reliant on the defense to begin with), SLG, and wOBA, and those didn’t show a trend either. I may be overlooking something at this point, but it really seems that the spin rate of a sinker isn’t integral to its effectiveness.

There are some other differences between the sinkers of the players labeled above, however. In our first exploration into spin rates I mentioned that how the spin is applied is another important aspect of pitch design, and sinkers might be the perfect pitch to demonstrate that point. First, let’s look at the spin profile of Lance Lynn’s sinker from the pitcher’s perspective. (I haven’t figured out how to get this image for specific pitches yet, so all the pitches in Lynn’s repertoire are listed. However, we’re only focused on the orange wedges that represent spin based on the observed movement of his sinker.)

The observed spin is almost completely horizontal, spinning from 3 to 9 o’clock on the graph. This means very little spin is going towards resisting gravity (more sink) and most of the spin is creating arm-side run. This bears out when we look at Lynn’s sinker movement from 2021.

Lynn’s sinker produces 12 inches of arm-side movement and drops just over 24 inches. Statcast has his sinker at a -7 run value (above average). Hitters hit for a .329 wOBA and a 32.8% hard-hit percentage against the pitch. Now, compare this profile to Miles Mikolas’ sinker:

A much larger portion of Mikolas’ sinker spin goes toward the top of the ball. This should translate into less sink compared to Lance Lynn’s sinker, and we see from Baseball Savant that that is indeed the case (due to Mikolas’ injuries in 2020 and 2021, I took the liberty of including his 2019 sinkers to make up for the small 2021 sample size).

How does Mikolas’ sinker compare to Lynn’s? Baseball Savant has Mikolas’ sinker at a run value of 2 (just below average). Opponents hit for a .368 wOBA against the pitch and a 50% hard-hit rate in 2021. Granted, again, the 2021 sample is pretty small, but the 2021 numbers look pretty similar to his 2019 numbers for his sinker. This provides some evidence that how spin is applied to a sinker is more important than the spin rate itself.

It does still feel like something is being overlooked in this analysis, though. One counter to this argument is Steven Matz’s sinker, which has more vertical observed spin than Mikolas’ has, yielding both less arm-side run and less sink. However, he has a higher whiff rate and strikeout rate with his sinker than Lynn does. The trade-off is that Matz’s sinker gets hit harder than Lynn’s when contact gets made. Baseball Savant has both pitches at a -7 run value, identical by that metric despite their different profiles.

The only takeaway I can give for sure is that analysing pitch design is dang difficult. Sinkers in particular offer a tough challenge since they’re designed to induce soft contact on the ground, putting the outcome into the hands of the defense. This puts us at a disadvantage, as our analysis as it’s been framed in the last few pieces just isn’t conducive to analyzing balls in play in the first place. That’s something I’ll have to look deeper into. Seam-shifted wake might also have something to do with the unexpected results as well, but I don’t have an opener big enough for that can of worms at this point.

I am comfortable saying that all things considered, I’d rather have a sinker that looks like Lynn’s. It is very possible that Mikolas or Matz could end up with the “better” sinker in 2022 just due to how ridiculously good the Cardinals’ infield is defensively, but, in my opinion, it’s impossible to say by raw numbers that their sinkers are objectively better than Lynn’s based on spin direction and movement.

I’m still trying to hammer out the flaws in the process, but it’s tough to get back to looking at the forest when you’re in all the trees. So questions, comments, and criticism on the methods for the analysis are, as always, heavily encouraged and appreciated.