Unraveling ‘spin rate’ in baseball: How much does it really matter?

Dissecting the curveball from the Royals’ Ian Kennedy

Kansas City Royals pitcher Ian Kennedy has been throwing his curveball better this year, but hitters are both hitting it and whiffing at it. Video by John Sleezer and Maria Torres/The Kansas City Star
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Kansas City Royals pitcher Ian Kennedy has been throwing his curveball better this year, but hitters are both hitting it and whiffing at it. Video by John Sleezer and Maria Torres/The Kansas City Star

Every time the Wizards of Analytics roll out a new metric, a certain segment of fans react as if we’ve discovered the Rosetta Stone of Baseball.

Those fans believe “launch angle” reveals the right way to hit a baseball, even though the Houston Astros — currently holding the best team batting average in baseball – are hitting .078 when they hit a fly ball that isn’t a home run, and it’s pretty clear hitters without consistent power should keep the ball out of the air and focus on line drives and grounders.

Those same observers believe “sprint speed” reveals baseball’s fastest players, even though it’s measured in one-second bursts and a slower runner who makes better turns could beat a runner with superior sprint speed around the bases.

Those fans believe “ultimate zone rating” reveals the best defenders, even though metrics advocates admit its video scouts (people watching baseball on TV) and its methodology aren’t quite as precise as the numbers might lead you to believe, and may not represent what actually happened on the field.

And now we once again have a metric being treated like it’s carved on stone tablets: “spin rate.”

Spin rate is the number of times a pitched baseball revolves on its way to home plate, measured in revolutions per minute. Here’s what’s glossary has to say about it:

“As more data have become available, most experts have agreed that fastballs and breaking balls are tougher to hit when they possess higher Spin Rates.”

What could be simpler?

The higher the spin rate, the better the fastball, curve or slider.

But do a Statcast search of all the pitchers who threw at least 1,000 pitches last season, eliminate all the pitches that weren’t fastballs or breaking balls, and you get some interesting results. Some 268 names pop up.

And despite’s pronouncement that high spin rate makes for a better heater or breaking pitch, some of the pitchers who rank near the top of the average spin rate list still had mediocre seasons.

  • Sergio Romo: sixth-best spin rate in baseball, ERA of 4.14.
  • Chris Stratton: seventh-best spin rate in baseball, ERA of 5.09.
  • Tyson Ross: 10th-best spin rate in baseball, ERA of 4.15.

These guys threw fastballs or breaking pitches around nine times out of 10 — in Ross’s case, more like 9.9 times out of 10 — and their high spin rate was no guarantee of success.

Did a low spin rate guarantee failure?

Head for the bottom of the list and you find pitchers with below-average spin rate with above-average results.

  • Jared Hughes: 264th-best spin rate in baseball, ERA of 1.94.
  • Blake Parker: 267th-best spin rate in baseball, ERA of 3.26.
  • Yoshihisa Hirano: 268th-best spin rate in baseball, worst on the list, ERA of 2.44.

Same thing with the pitchers at the top of the list: More than 90 percent of the time these guys threw the type of pitches that a high spin rate is supposed to improve, but threw them with low spin rate and still had success.

How do you explain the contradiction?

A pitching coach who has worked with big-league teams in the past and whose name will be left out here because he might want to work with big-league teams in the future offered up an explanation.

Depending on the spin rate’s axis — a can of worms we’ll leave unopened for now — a pitcher with high spin rate should have success working up in the zone; his high fastball should have good life when thrown letter-high.

A pitcher with low spin rate should have success working down in the zone — his fastball should have good sink when thrown knee-high.

And average spin rate should result in average stuff.

So far, so good.

But 268 pitchers were on the list and No. 134 — pretty much smack-dab in the middle — was Wade Miley with an ERA of 2.57; No. 137 was Stephen Strasburg with an ERA of 3.74; and No. 139 was Brad Keller, the young Kansas City Royals ace, with an ERA of 3.08.

So guys with high-average spin rate could still pitch poorly and guys with low-average spin rate could still pitch well and guys with average-spin rate could still get above-average results.

And to make it even more confusing, remember this: If a pitcher can change his spin rate from pitch to pitch — and there’s some dispute about that, too — a guy who threw half his pitches with above-average spin rate and half his pitches with below-average spin rate could wind up with an overall average spin rate.

So what, if anything, does spin rate actually tell us?

It’s not the only thing that matters.

Our anonymous pitching coach thought spin rate was best used as a tool for analyzing how a pitcher should use the stuff he has: Which pitches in which location(s) would be most effective with this guy’s spin rate?

He also thought baseball in general was going way overboard in its use of new metrics. They matter, he said, but should be used to complete a larger picture that is composed of everything that matters.

Talk to people who throw and receive pitches for a living and don’t be surprised if they say the most important thing, by far, is location. And that the second-most important thing ain’t close.

A pitcher could have a higher spin rate than a White House press secretary, and if he threw that high spin-rate pitch down the middle, it would still get whacked lopsided. If a pitcher with lousy spin rate hits the mitt down and away, that’s still a tough pitch to hit.

So, once again, does spin rate actually matter?

It’s hard to imagine it doesn’t. All the characteristics of a thrown pitch matter, but other things matter as well. Location, velocity, pitch sequence, slide steps, position on the rubber and the ability to hide the ball during the windup are just some of the things that immediately come to mind.

It’s never just one thing.

You can’t look at launch angle and know who’s a good hitter, you can’t look at sprint speed and know who’s the fastest runner and you can’t look at spin rate and know who’s a good pitcher.

It’s more complicated than that.

If you feel like you know less now than you did when you started reading this article, good. You’re making progress.

You can’t learn anything if you already know everything.

One of the things that will irritate a big-league ballplayer faster than jock itch is someone who has never played the game thinking they’ve got the game figured out. The people who stand on the dirt know they need to always be in learning mode because nobody knows everything ... and the first step toward getting smarter is admitting all the things you don’t know.

Admitting spin rate doesn’t tell you everything you need to know about pitching is a good step forward.

So take it.

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