by Matt Wilkes

A closer look at the Reds’ elite pitch-spinners

Since the dawn of baseball, pitchers have tried to generate spin to get more movement. But until recent years, there’s been no way to measure it or determine exactly how important it is.

Pitch tracking systems such as Trackman and Statcast have brought spin rate to the forefront of baseball analytics. The Astros have assembled a pitching staff full of players who can spin the ball with the best of the best, including 2019 All-Stars Justin Verlander, Gerrit Cole, and Ryan Pressly. They recently acquired Aaron Sanchez, who has one of the best curveball spin rates in the game. Lance McCullers Jr., currently on the injured list as he recovers from Tommy John surgery, can spin the curveball with the best of ’em as well.

The Reds have started to take a similar approach in targeting high-spin pitchers.

Sonny Gray, of course, is the most notable example. Baseball analysts have raved over Gray’s curveball from the day he debuted with the Oakland Athletics in 2013. Few pitchers in the game get more spin than the right-hander. Gray’s four-seam fastball averages 2,512 revolutions per minute, placing him in the 91st percentile in baseball. His slider (2,843) and curveball (2,952) are even better, ranking in the 95th and 97th percentile, respectively. Trevor Bauer also has an elite slider in terms of spin rate (2,728).

Despite a challenge from Bauer with the slider, there aren’t many pitchers in MLB better at spinning the ball than Gray. One of those pitchers, though, is on the same team. It’s not Luis Castillo, Michael Lorenzen, Raisel Iglesias, or another pitcher you may immediately suspect.

It’s Lucas Sims.

Sims’ four-seam fastball and curveball rank in the 99th (!) percentile. Sims gets more spin than all but eight pitchers in baseball with his fastball (2,623 rpm). For reference, 702 players have thrown a four-seamer this year.

Only Pressly, Dillon Maples, and Seth Lugo get more spin on their curveballs than Sims (3,116 rpm) out of 425 pitchers. This ability is one reason Sims was a top prospect and why the Reds targeted him when they traded Adam Duvall to the Braves in July 2018.

But what do these elite spin rates mean for Gray, Sims, and Bauer? To answer that question, let’s dissect its implications for fastballs and breaking pitches.

Four-Seam Fastball

We’ve discussed high-spin fastballs a few times at RC+, most recently when Steve Mancusco broke down an at-bat between Michael Lorenzen and Mike Trout. Go check that out as well.

As a refresher, a four-seamer with high backspin has more “rise” than an average fastball. That does not mean it literally rises like a wiffle ball — gravity makes that impossible from a normal arm angle. Moreover, an MLB mound is 10 inches above the rest of the field, so the pitcher has to throw on a downward plane toward the batter.

Rise simply means the fastball drops less than a lower-spin one due to the Magnus force. I’ll let Driveline Baseball explain the physics behind that one:

“[T]he faster the backspin the faster the air is deflected downwards and the higher the force pushing the ball back upward.”

Professional hitters have seen thousands of fastballs in their careers. They’ve come to expect a certain amount of drop. As a result, they’re more likely to swing under a high-spin fastball, particularly if it’s up in the strike zone. If they make contact, they’re more likely to pop it up. This is why a low-spin fastball can be effective, too — it drops more than average and results in more ground balls. An average spin rate gets pitchers into trouble with their four-seam fastball because it doesn’t rise or drop enough to fool hitters.

Consider this: The league average spin rate of a four-seam fastball is 2,286 rpm. Pitches above that mark get an 11.4% swinging-strike rate and a 10.5% pop-up rate, while those below average sit at 8.9% and 8.5%. As spin rates get further from the average, the differences become more stark, especially with swings and misses.

Spin rate for a four-seamer also tends to increase as velocity does, although high velocity does not necessarily equate to high spin. A high-velocity fastball with a low spin rate may not be as effective as a low-velo heater with a high spin rate. Driveline Baseball created Bauer Units — named after Trevor Bauer — to measure this. The equation is simply spin rate divided by velocity. Here is the basic premise behind the stat:

“This enables us to normalize the spin per the velocity of the pitch. If a pitcher is spinning a fastball at 2400 RPM, that is less impressive at 99 MPH and much more impressive at 89 MPH.”

League average in 2019 is 24.5. In general, a pitcher with high BU should throw their four-seamer up in the zone, and one with low BU should throw low in the zone.

Gray and Sims throw their fastballs at almost the same velocity — 93.4 and 93.2 mph, respectively. Gray is exactly at league average. Unsurprisingly, both rank well above average in Bauer Units. Sims sits at 28.2, while Gray is at 26.9.

With that information in mind, let’s see how their four-seamers have performed.

We have quite the discrepancy in results. Sims has allowed a worse slugging percentage and wOBA, but his expected metrics are significantly better than Gray’s. Sims also misses far more bats and gets more weak pop-ups than Gray. Simply having a higher Bauer Units score doesn’t account for this difference. We need to look at the way each pitcher uses his four-seam fastball.

Remember, a pitcher with above average Bauer Units on a four-seamer should throw the pitch up in the zone. Sims has clearly done that more than Gray. Additionally, Sims has used the upper part of the zone in the middle of the plate, which is important for tempting batters into swinging. This video shows a perfect example of that. Sims throws a four-seamer at 2,670 rpm above the strike zone, and Johan Camargo swings right underneath it for strike three.

Hitting the corners is good for getting called strikes, but it doesn’t result in as many swings. Moreover, a fastball lower in the zone is more likely to fall right in the hitter’s bat path, especially in today’s game with so many uppercut swings. When Gray has thrown his fastball up, his SwStr% jumps to 12.6%. This video shows Gray striking out Eric Thames with a high heater coming in at 2,628 rpm.

We also have to consider movement. With a four-seamer, we’re worried about vertical movement when it comes to getting swings and misses. A pitch with a lot of spin and a lot of movement has a high “spin efficiency.” You may also see this called “transverse spin” or “useful spin.” A pitch with a lot of spin but no movement is said to have “gyrospin,” just like a football with a tight spiral or a bullet firing out of a gun, which equates to little movement. This is also called “parallel spin.” The difference between useful spin and non-useful comes down to the axis or tilt of the pitch.

According to Statcast’s pitch movement leaderboards, Sims gets 1.9 more inches of vertical movement compared to other pitchers who throw at a similar velocity and from a similar arm angle. Again, this doesn’t mean that Sims’ fastball literally rises but that it drops less than an average fastball (check out this link for a visualization). That puts him 51st among 421 qualified pitchers. We can say Sims is probably generating efficient spin.

Gray gets 0.6 fewer inches than average. This also goes a long way toward explaining the differences between the results of the two pitchers. It means Sims’ fastball gets more rise and, thus, more swings and misses; it has a high spin efficiency. Gray’s fastball has a lower spin efficiency, something he talked about with The Athletic before the season.

“You normally want to throw them high, but what happens is that mine doesn’t have that ride, that extra life on the ball, because of the 45 percent spin efficiency on my fastball. So you might not want to throw the four-seam high if your spin efficiency is low.”

Now we see the reason Gray is throwing his fastball lower in the zone and on the corners. While Gray has elevated other parts of his game as a member of the Reds, getting better efficiency on his fastball remains a challenge. He has improved his vertical movement from 1.4 inches below average last year with the Yankees, so there has been some progress.


In essence, a 12-6 curveball is the opposite of a four-seam fastball. Rather than backspin, pitchers are trying to put topspin on the ball. Most curveballs, however, are not true 12-6 pitches and have some degree of horizontal movement.

A curve with high spin (and spin efficiency, of course) will have significantly more downward movement. It will get plenty of whiffs, yes, but also ground balls. In contrast, a low spin rate on a curveball generally means less movement and more fly balls. When these pitches are hung over the plate, it doesn’t end well for the pitcher.

Curveballs get more spin than four-seam fastballs, averaging 2,529 rpm league-wide this season. Curves with above-average spin get a 12.8% swinging-strike rate and a 49.6% ground-ball rate. Curves with below average spin sit at an 11.4 SwStr% and a 44.4 GB%. Here’s what those numbers look like as spin rate gets higher and lower than average:

Gray and Sims also throw their fastballs at almost identical velocities — 81.8 and 81.7 mph, respectively. Because he generates similar velocity with a higher spin rate, Sims gets more Bauer Units (38.1). Gray still comes in well above league average (32.2), however, at 36.1 BU. Both have a nice mix of spin and velocity.

Here’s a look at the results both are getting with their curveballs:

The curveball is clearly a dominant pitch for both Sims and Gray, with the former edging out the latter in all but ground-ball rate. Gray ranks a bit below average when it comes to missing bats — the slider is his go-to pitch when he needs a whiff — but he more than makes up for it by getting a ridiculous number of grounders. Thirty-one pitchers have had at least 50 curveballs put into play against them, and only four have a higher GB%: Rich Hill, the late Tyler Skaggs, Matt Barnes, and Merrill Kelly.

Both pitchers get more horizontal movement than average with their curveballs. Gray ranks 15th among all MLB pitchers at 6.6 inches above average. Sims comes in at 2.5 inches above average. While Sims gets below average drop, Gray gets 3.2 more inches of vertical movement than average. Gray is one of only 14 pitchers who generates at least three inches of vertical and horizontal movement above the league average.

Here’s what Gray’s curveball looks like:

And here’s a taste of a Sims curve:

Spin rate isn’t everything for a curveball. Trevor Bauer gets more vertical movement on his curveball than any other pitcher, but he has mediocre overall spin (51st percentile). Rather than trying to get more raw spin, he has focused on perfecting his spin axis to achieve more movement. The result is a beautiful 12-6 curveball:


While a curveball typically has topspin, a slider has more side-spin. Higher spin ideally results in more horizontal movement. However, high spin efficiency is extremely difficult to achieve with a slider. Most have a high degree of gyrospin and do not move as much as curveballs — those that do are usually dubbed “slurves.” Some sliders, like Amir Garrett’s, get little spin or movement and still baffle hitters.

Why is a slider still effective even when it has a low spin efficiency? It’s all about playing it off the fastball. I’ll turn that explanation over to Rockland Peak Performance:

“The idea is to have different pitches with different degrees of movement thrown in a mix.  In the case of a typical slider you are throwing a ball with less movement than most, and gravity is pulling on it with less negating Magnus Force.  So, it’s going to “break” and drop quicker than a typical fastball with usually has a rise component due to back spin.”

But spin isn’t meaningless for a slider, either. “Slurvy” pitches often have higher spin rate and efficiency, and that comes with more movement. Because sliders can succeed with low or high spin, we see less of a discrepancy in this table (for reference, league average is 2,424 rpm):

This starts to clarify why Gray uses his breaking balls as he does. Sliders get only an average rate of ground balls no matter the spin. Whiffs are the prize for throwing sliders, especially when they have more spin. That being said, batters whiff nearly one-third of the time they swing at even low-spin sliders. There’s a reason more sliders are being thrown than ever before.

Both Gray and Bauer throw wicked sliders with elite movement. Gray is elite in both horizontal (10.2 inches above average) and vertical movement (6.1 inches above average), ranking third and 12th, respectively, among all pitchers. Bauer, who completely revamped his slider after the 2017 season, ranks seventh in horizontal movement (8.2 inches above average). We’re talking serious spin efficiency here.

Here’s Gray:

And here’s Bauer:

No surprise — their sliders are incredibly hard to hit:

Both miss tons of bats with their sliders. When hitters swing, they’re missing nearly half the time. Among 79 starting pitchers with 150 swings on sliders this season, Bauer is ninth and Gray is 12th in whiff rate.

Heatmaps clearly show the reason behind the difference in ground-ball rate for the two pitchers on their sliders.

Gray throws his slider down in the zone more often, which obviously results in more ground balls when batters make contact. Bauer appears to make it a point to induce chases more than anything else. His slider starts in the heart of the plate — appearing as a juicy fastball right down the middle — before breaking outside.

Velocity is important for a slider as well. Ideally, it sits about 8 mph lower than the fastball — quick enough that it still looks like a fastball but not slow enough that it’s easy to identify. Bauer throws a much slower slider (79.5 mph) than Gray (84.7), thus having the advantage in the stat that bears his name (34.3 BU vs. 33.6). League average is 28.7, so both pitchers come out well ahead.


Spin rate isn’t an automatic key to success. Many other components go into a successful pitcher. But if a player learns to harness elite spin and find the right axis through an ideal grip, arm angle, and release point, they can translate it all into a dominant pitch. Bauer has been an example of that time and time again in his major-league career. Sonny Gray has clearly mastered it with his breaking pitches and turned in one of his best MLB seasons. Using Rapsodo cameras and the expertise of Derek Johnson and Caleb Cotham, Reds pitchers like Sims can get the most out of their spin rates.

Matt Wilkes got hooked on Reds baseball after attending his first game in Cinergy Field at 6 years old, and he hasn’t looked back. As a kid, he was often found imitating his favorite players — Ken Griffey Jr., Adam Dunn, Sean Casey, and Austin Kearns — in the backyard. When he finally went inside, he was leading the Reds to 162-0 seasons in MVP Baseball 2005 or keeping stats for whatever game was on TV. He started writing about baseball in 2014 and has become fascinated by analytics and all the new data in the game. Matt is also a graduate of The Ohio State University and currently lives in Columbus. Follow him on Twitter at @_MattWilkes.

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The Hessenauer Corporation

Thanks for the very informative article!