This article is part of our The Saber's Edge series.
The folks at MLB Advanced Media have a great new statistic they have pushed out recently — pitch spin rate. Just a few days ago, they showed that Yu Darvish's four-seam fastball has one of the league's highest spin rates. In 2013, we didn't need to know Darvish's spin rate to understand his fastball was a good pitch with him striking out 11.4 batters per nine innings. I can understand why someone could be skeptical of spin rates. I am. The following is a shallow dive into a deep topic to help get a bit of an understanding of spin rates and what information can be useful.
What does the spin rate actually tell us that we already don't know with sites like FanGraphs and BrooksBaseball having a ton of information on each pitch? Besides the spin rate, other factors go into the quality of a pitch like velocity, location, deception, release point and other pitches in the pitcher's arsenal. Additionally, some work has already been done on the subject by FanGraphs' Jonah Pemstein in a two-part series. For each pitch type, he found the contact rate, swing rate, groundball rate, pop-up rate, BABIP and overall value. The post was extremely information heavy, but few new conclusions were provided.
I will start my own study with the basics with the two most common pitches getting mentioned, four-seam fastball and curveballs.
Effects of Spin Rate on Four-Seam Fastballs
The basic fastball is a great place to start because
What does the spin rate actually tell us that we already don't know with sites like FanGraphs and BrooksBaseball having a ton of information on each pitch? Besides the spin rate, other factors go into the quality of a pitch like velocity, location, deception, release point and other pitches in the pitcher's arsenal. Additionally, some work has already been done on the subject by FanGraphs' Jonah Pemstein in a two-part series. For each pitch type, he found the contact rate, swing rate, groundball rate, pop-up rate, BABIP and overall value. The post was extremely information heavy, but few new conclusions were provided.
I will start my own study with the basics with the two most common pitches getting mentioned, four-seam fastball and curveballs.
Effects of Spin Rate on Four-Seam Fastballs
The basic fastball is a great place to start because it is the pitch in which every other pitch must build off. A big key with the four-seamer is its wide range of values from the Jered Weaver 83 mph fastball to the lightning-bolt Aroldis Chapman 103 mph heater. A pitch's velocity is a huge factor when determining how this pitch will perform. For this reason, velocity was added to the analysis.
To get a basic reference on how different spinning fastball work, I binned spin rate and velocity and found what I see as the three most important individual pitch stats: swinging strikes (strikeouts), groundballs (usually singles at best) and popups (easy outs). To minimize outliers, each grouping had to have a minimum 50 pitches.
Note: The best way I have found to find individual pitchers and their spin rate is this table at Baseball Savant.
Number of Samples
| SPIN | ||||||||||||
| VELOCITY | 1600 | 1700 | 1800 | 1900 | 2000 | 2100 | 2200 | 2300 | 2400 | 2500 | 2600 | 2700 |
| 83 | 67 | 93 | 116 | 95 | 50 | 53 | ||||||
| 84 | 57 | 106 | 156 | 222 | 160 | 154 | 67 | |||||
| 85 | 56 | 75 | 174 | 239 | 267 | 250 | 161 | |||||
| 86 | 51 | 195 | 319 | 426 | 528 | 503 | 392 | 115 | ||||
| 87 | 120 | 347 | 624 | 871 | 1146 | 1098 | 867 | 347 | ||||
| 88 | 97 | 267 | 689 | 1367 | 1943 | 2438 | 2330 | 1734 | 639 | 130 | ||
| 89 | 62 | 149 | 451 | 1192 | 2433 | 3652 | 4183 | 3684 | 2715 | 1024 | 247 | |
| 90 | 54 | 182 | 628 | 1638 | 3709 | 6174 | 7559 | 6278 | 4189 | 1576 | 358 | 70 |
| 91 | 194 | 681 | 1708 | 4714 | 8448 | 10983 | 9981 | 6262 | 2260 | 611 | 126 | |
| 92 | 61 | 185 | 582 | 1899 | 5158 | 10017 | 13835 | 14018 | 9725 | 3864 | 952 | 222 |
| 93 | 56 | 159 | 443 | 1571 | 5002 | 9752 | 14015 | 15756 | 11727 | 5310 | 1476 | 230 |
| 94 | 129 | 385 | 1281 | 3940 | 8415 | 12934 | 14928 | 11317 | 5978 | 2003 | 361 | |
| 95 | 67 | 211 | 747 | 2677 | 6220 | 10120 | 12026 | 9704 | 5468 | 2110 | 412 | |
| 96 | 93 | 351 | 1544 | 4354 | 7243 | 9093 | 7929 | 4564 | 1719 | 384 | ||
| 97 | 107 | 766 | 2326 | 4080 | 5288 | 5393 | 3246 | 1126 | 229 | |||
| 98 | 269 | 1132 | 2106 | 2818 | 3116 | 2160 | 735 | 125 | ||||
| 99 | 74 | 354 | 884 | 1219 | 1358 | 997 | 431 | 71 | ||||
| 100 | 72 | 260 | 406 | 406 | 401 | 200 |
Swinging Strike Rate
| SPIN | ||||||||||||
| VELOCITY | 1600 | 1700 | 1800 | 1900 | 2000 | 2100 | 2200 | 2300 | 2400 | 2500 | 2600 | 2700 |
| 83 | 0.0% | 1.1% | 4.3% | 11.6% | 10.0% | 5.7% | ||||||
| 84 | 1.8% | 2.8% | 4.5% | 5.9% | 3.8% | 7.1% | 10.5% | |||||
| 85 | 0.0% | 0.0% | 3.5% | 3.4% | 5.2% | 3.6% | 4.4% | |||||
| 86 | 5.9% | 3.1% | 2.8% | 5.9% | 4.7% | 4.0% | 5.9% | 8.7% | ||||
| 87 | 5.0% | 2.0% | 3.5% | 4.3% | 4.9% | 4.6% | 5.1% | 6.6% | ||||
| 88 | 5.2% | 3.4% | 4.4% | 4.0% | 4.3% | 4.3% | 5.4% | 7.5% | 6.9% | 8.5% | ||
| 89 | 4.8% | 2.0% | 3.3% | 4.3% | 5.5% | 3.5% | 5.1% | 5.7% | 5.9% | 6.0% | 8.9% | |
| 90 | 1.9% | 5.5% | 4.1% | 3.5% | 4.6% | 5.0% | 5.3% | 5.6% | 7.5% | 8.4% | 10.3% | 4.3% |
| 91 | 7.9% | 4.1% | 3.7% | 3.9% | 4.8% | 5.4% | 6.5% | 6.8% | 6.8% | 7.8% | 9.2% | 7.9% |
| 92 | 7.0% | 4.1% | 5.2% | 5.2% | 5.9% | 6.5% | 7.1% | 7.6% | 8.3% | 8.7% | 10.4% | |
| 93 | 1.8% | 1.9% | 4.1% | 5.2% | 5.2% | 6.9% | 6.7% | 7.5% | 8.3% | 9.6% | 9.6% | 12.2% |
| 94 | 5.6% | 3.9% | 3.1% | 5.2% | 5.6% | 6.8% | 7.4% | 7.9% | 8.5% | 9.2% | 10.9% | 11.4% |
| 95 | 1.5% | 4.7% | 6.6% | 6.4% | 7.3% | 8.1% | 8.7% | 10.1% | 10.0% | 12.0% | 12.4% | |
| 96 | 14.0% | 6.8% | 5.9% | 7.4% | 8.9% | 9.3% | 10.2% | 10.8% | 11.3% | 12.5% | ||
| 97 | 4.7% | 7.4% | 7.8% | 8.9% | 9.8% | 10.9% | 12.8% | 13.6% | 19.2% | |||
| 98 | 8.2% | 7.6% | 9.3% | 10.5% | 11.7% | 13.2% | 13.3% | 16.8% | ||||
| 99 | 5.4% | 10.2% | 9.1% | 11.2% | 12.8% | 13.4% | 16.0% | 19.7% | ||||
| 100 | 9.7% | 11.2% | 9.1% | 14.3% | 17.2% | 18.0% |
Groundball Rate
| SPIN | ||||||||||||
| VELOCITY | 1600 | 1700 | 1800 | 1900 | 2000 | 2100 | 2200 | 2300 | 2400 | 2500 | 2600 | 2700 |
| 83 | 33.3% | 17.7% | 44.4% | 30.0% | 33.3% | 28.6% | ||||||
| 84 | 44.4% | 60.0% | 45.8% | 53.2% | 26.7% | 33.3% | 8.3% | |||||
| 85 | 15.4% | 50.0% | 48.5% | 42.6% | 34.5% | 28.6% | 33.3% | |||||
| 86 | 45.5% | 31.4% | 39.1% | 29.3% | 36.1% | 22.2% | 18.9% | 35.0% | ||||
| 87 | 48.2% | 39.0% | 34.4% | 38.8% | 35.6% | 30.7% | 28.4% | 30.4% | ||||
| 88 | 48.0% | 37.8% | 40.7% | 40.8% | 34.4% | 32.5% | 28.6% | 32.9% | 25.5% | 28.6% | ||
| 89 | 61.5% | 43.8% | 52.5% | 39.7% | 37.1% | 38.4% | 35.0% | 30.6% | 27.5% | 38.9% | 44.7% | |
| 90 | 46.2% | 60.5% | 50.0% | 46.8% | 40.4% | 35.9% | 34.0% | 30.1% | 28.6% | 26.0% | 36.8% | 46.2% |
| 91 | 25.0% | 36.7% | 48.4% | 39.3% | 37.7% | 35.6% | 35.6% | 33.8% | 31.4% | 28.3% | 34.7% | 30.0% |
| 92 | 63.4% | 54.5% | 44.9% | 39.2% | 35.9% | 35.3% | 33.5% | 32.4% | 32.2% | 29.1% | 32.0% | |
| 93 | 33.3% | 59.1% | 52.3% | 40.2% | 45.1% | 39.1% | 35.0% | 33.9% | 33.1% | 28.5% | 32.8% | 38.9% |
| 94 | 33.3% | 37.5% | 44.4% | 43.7% | 44.8% | 41.2% | 38.7% | 37.0% | 36.2% | 33.6% | 30.6% | 35.7% |
| 95 | 40.0% | 52.9% | 47.0% | 46.1% | 42.8% | 40.2% | 37.0% | 35.9% | 31.2% | 31.2% | 32.8% | |
| 96 | 45.5% | 52.6% | 52.4% | 44.2% | 40.2% | 38.5% | 36.0% | 37.0% | 31.0% | 37.7% | ||
| 97 | 73.9% | 51.7% | 42.2% | 46.2% | 39.5% | 41.1% | 38.6% | 36.1% | 31.4% | |||
| 98 | 60.3% | 46.1% | 41.6% | 41.9% | 41.6% | 38.0% | 35.1% | 43.8% | ||||
| 99 | 76.9% | 50.7% | 44.1% | 47.7% | 48.5% | 43.1% | 40.0% | 33.3% | ||||
| 100 | 73.3% | 50.0% | 48.3% | 59.0% | 47.8% | 37.9% |
Popup Rate
| SPIN | ||||||||||||
| VELOCITY | 1600 | 1700 | 1800 | 1900 | 2000 | 2100 | 2200 | 2300 | 2400 | 2500 | 2600 | 2700 |
| 83 | 8.3% | 0.0% | 7.4% | 20.0% | 11.1% | |||||||
| 84 | 5.6% | 0.0% | 4.2% | 8.5% | 0.0% | 0.0% | 8.3% | |||||
| 85 | 0.0% | 10.0% | 3.0% | 13.0% | 10.3% | 14.3% | 8.3% | |||||
| 86 | 9.1% | 2.9% | 17.4% | 12.2% | 13.4% | 16.2% | 13.5% | 15.0% | ||||
| 87 | 7.4% | 8.5% | 6.6% | 10.9% | 9.6% | 9.4% | 9.2% | 12.5% | ||||
| 88 | 4.0% | 4.4% | 7.1% | 5.1% | 9.3% | 8.8% | 9.5% | 12.2% | 8.2% | 0.0% | ||
| 89 | 0.0% | 9.4% | 5.1% | 8.5% | 9.2% | 7.8% | 9.8% | 10.4% | 12.6% | 12.2% | 6.4% | |
| 90 | 15.4% | 7.0% | 4.6% | 6.1% | 6.3% | 7.6% | 9.2% | 10.0% | 11.6% | 10.9% | 3.5% | 7.7% |
| 91 | 0.0% | 6.1% | 3.1% | 4.6% | 7.3% | 8.6% | 8.7% | 10.2% | 10.0% | 12.9% | 9.5% | 10.0% |
| 92 | 0.0% | 2.0% | 2.8% | 7.3% | 8.0% | 8.5% | 10.0% | 11.4% | 11.3% | 18.9% | 24.0% | |
| 93 | 0.0% | 2.3% | 4.6% | 4.3% | 6.6% | 7.7% | 8.2% | 8.9% | 9.6% | 9.9% | 11.6% | 2.8% |
| 94 | 0.0% | 3.1% | 0.0% | 4.4% | 6.4% | 8.3% | 7.4% | 8.3% | 9.4% | 10.9% | 11.8% | 7.1% |
| 95 | 10.0% | 2.9% | 5.4% | 7.1% | 5.9% | 7.7% | 9.6% | 9.1% | 10.1% | 10.9% | 17.2% | |
| 96 | 0.0% | 6.4% | 5.5% | 6.3% | 7.0% | 8.2% | 9.6% | 8.6% | 12.6% | 13.2% | ||
| 97 | 8.7% | 6.9% | 4.7% | 6.2% | 6.9% | 7.0% | 10.2% | 5.9% | 8.6% | |||
| 98 | 3.5% | 4.2% | 3.8% | 6.1% | 7.1% | 8.1% | 8.1% | 6.3% | ||||
| 99 | 0.0% | 5.8% | 4.0% | 7.0% | 5.9% | 11.0% | 16.7% | 16.7% | ||||
| 100 | 6.7% | 5.3% | 10.0% | 7.7% | 4.4% | 13.8% |
First off, not all the numbers make a nice transition from one value to the next, so a person may need to massage the numbers from those around it to get a reasonable value.
As for the results, the output of the swinging strike table is so important, you should stop and bookmark this page now. The big item to notice is that if a pitch has enough of a spin rate, it can make up for being quite a bit slower. Let's compare two pitches. Pitcher A's fastball averages 90 mph on his pitches with an average spin of 2,400 rpm. Pitcher B averages 96 mph and 2,100 rpm on his spin. Looking at the above tables, these could easily be the expected values:
Fastball A:
Swstr%: 7.3%
Popup%: 11%
GB%: 30%
Fastball B
SwStr%: 7.3%
Popup%: 5.5%
GB%: 44%
These fastballs will generate the same amount of swinging strikes even though one is 6 mph slower than the other. The key in evaluating this pair is to decide if the team would like twice as many sure outs with the easy popups or try to field a few more groundballs. Looking through some pitchers, I found some comps for the two pitches. Fastball A is similar to Marco Estrada's and Fastball B is like Gerrit Cole's. Here are the actual results on the two fastballs.
Estrada (90 mph, 2,400 rpm)
Swstr%: 7.5%
Popup%: 13.7%
GB%: 27%
Cole (96 mph, 2,100 rpm)
Swstr%: 6.3%
Popup%: 5.6%
GB%: 48.5%
The numbers almost perfectly lineup with the expected values with the exception that Cole's fastball gets a few less than expected swinging strikes.
I think the biggest advantage with these numbers is to find pitchers with who have their fastball graded mainly off their fastball velocity. Their spin rate may move them up or down the quality pitch spectrum.
For a reference, here are the average spin values at each velocity.
| VELOCITY | AVG SPIN |
| 86 | 2188 |
| 87 | 2204 |
| 88 | 2198 |
| 89 | 2192 |
| 90 | 2197 |
| 91 | 2212 |
| 92 | 2234 |
| 93 | 2253 |
| 94 | 2269 |
| 95 | 2287 |
| 96 | 2303 |
| 97 | 2320 |
| 98 | 2338 |
| 99 | 2357 |
| 100 | 2382 |
Another use for the above tables is to get an idea of how a pitcher likely will produce if his spin and/or velocity changes. More than likely, a pitcher will see both his velocity and spin drop at the same time and fastball will be at a new lower level of production.
The key with fastball spin rate is to put it into context with the velocity. One or the other is not enough to determine the quality of the pitch. Enough with the fastballs, it's time to move onto curveballs.
Effects of Spin Rate on Curveballs
Curveballs seem to get a ton of love from the StatCast disciples. I think the main reason is because of the crazy high spin rates compared to fastballs.
For curveballs, I did the same binning of velocity and spin rate to find swinging strike rate and groundball rate. I ran the popup rates and the only information I found was a lack of information so their numbers are ignored. On to the tables.
Number of Samples
| SPIN | ||||||||||||
| VELOCITY | 1900 | 2000 | 2100 | 2200 | 2300 | 2400 | 2500 | 2600 | 2700 | 2800 | 2900 | 3000 |
| 68 | 60 | 48 | 102 | 137 | 56 | |||||||
| 69 | 39 | 72 | 95 | 92 | 86 | 141 | 81 | |||||
| 70 | 58 | 99 | 127 | 132 | 132 | 143 | 119 | |||||
| 71 | 78 | 140 | 192 | 212 | 220 | 284 | 209 | 96 | ||||
| 72 | 111 | 180 | 267 | 347 | 342 | 454 | 446 | 205 | 126 | 51 | ||
| 73 | 50 | 111 | 213 | 400 | 549 | 463 | 589 | 654 | 379 | 218 | 103 | |
| 74 | 105 | 179 | 286 | 479 | 728 | 638 | 674 | 831 | 555 | 398 | 244 | 75 |
| 75 | 123 | 251 | 345 | 467 | 807 | 842 | 848 | 922 | 732 | 570 | 324 | 131 |
| 76 | 153 | 318 | 474 | 591 | 898 | 1006 | 992 | 965 | 853 | 649 | 412 | 200 |
| 77 | 162 | 376 | 565 | 807 | 975 | 1158 | 1008 | 994 | 977 | 749 | 436 | 215 |
| 78 | 147 | 305 | 559 | 793 | 991 | 1165 | 1087 | 987 | 960 | 860 | 536 | 239 |
| 79 | 95 | 237 | 440 | 693 | 1037 | 1243 | 1043 | 837 | 802 | 836 | 554 | 323 |
| 80 | 70 | 163 | 379 | 634 | 907 | 1290 | 1116 | 820 | 706 | 600 | 400 | 251 |
| 81 | 74 | 137 | 293 | 544 | 759 | 1029 | 974 | 765 | 637 | 512 | 318 | 155 |
| 82 | 99 | 206 | 444 | 590 | 776 | 804 | 689 | 597 | 469 | 248 | 127 | |
| 83 | 51 | 173 | 287 | 456 | 548 | 551 | 558 | 450 | 315 | 184 | 82 | |
| 84 | 51 | 114 | 269 | 443 | 518 | 426 | 382 | 356 | 226 | 121 | 58 | |
| 85 | 64 | 146 | 285 | 337 | 302 | 221 | 228 | 142 | 70 | |||
| 86 | 93 | 149 | 179 | 128 | 101 | 99 | 97 |
Swinging Strike Rate
| SPIN | ||||||||||||
| VELOCITY | 1900 | 2000 | 2100 | 2200 | 2300 | 2400 | 2500 | 2600 | 2700 | 2800 | 2900 | 3000 |
| 68 | 3.3% | 8.3% | 11.8% | 12.4% | 14.3% | |||||||
| 69 | 0.0% | 4.2% | 6.3% | 5.4% | 15.1% | 8.5% | 9.9% | |||||
| 70 | 10.3% | 6.1% | 8.7% | 6.8% | 4.6% | 10.5% | 8.4% | |||||
| 71 | 7.7% | 8.6% | 6.3% | 6.1% | 9.1% | 5.6% | 8.6% | 10.4% | ||||
| 72 | 8.1% | 8.9% | 6.4% | 5.5% | 7.3% | 11.2% | 8.5% | 7.3% | 10.3% | 3.9% | ||
| 73 | 2.0% | 7.2% | 7.0% | 6.8% | 6.9% | 9.1% | 6.1% | 9.8% | 7.1% | 9.6% | 3.9% | |
| 74 | 1.9% | 3.9% | 7.7% | 7.9% | 7.8% | 9.1% | 9.8% | 7.1% | 9.4% | 8.0% | 7.4% | 6.7% |
| 75 | 4.1% | 6.8% | 7.5% | 9.2% | 7.8% | 7.6% | 8.5% | 7.6% | 9.4% | 8.8% | 7.1% | 6.9% |
| 76 | 2.0% | 6.9% | 6.8% | 6.9% | 7.7% | 9.2% | 10.7% | 6.8% | 7.5% | 7.1% | 8.7% | 9.0% |
| 77 | 5.6% | 4.8% | 4.4% | 8.7% | 7.6% | 7.2% | 8.8% | 9.7% | 5.5% | 9.0% | 7.6% | 7.0% |
| 78 | 6.1% | 9.5% | 8.1% | 8.1% | 7.2% | 8.7% | 9.9% | 8.4% | 9.2% | 9.8% | 8.8% | 11.7% |
| 79 | 7.4% | 5.5% | 6.6% | 6.9% | 7.7% | 6.8% | 9.7% | 8.0% | 8.7% | 8.1% | 11.7% | 11.8% |
| 80 | 8.6% | 7.4% | 7.7% | 7.7% | 11.3% | 7.7% | 8.7% | 9.0% | 7.7% | 10.8% | 12.0% | 10.4% |
| 81 | 5.4% | 4.4% | 6.5% | 9.9% | 9.4% | 10.0% | 12.6% | 7.2% | 9.7% | 6.6% | 9.8% | 11.6% |
| 82 | 5.1% | 9.7% | 12.4% | 11.0% | 11.2% | 9.8% | 9.6% | 8.7% | 9.6% | 11.7% | 10.2% | |
| 83 | 9.8% | 12.1% | 16.0% | 12.9% | 11.7% | 10.2% | 15.1% | 10.0% | 9.5% | 12.5% | 17.1% | |
| 84 | 11.8% | 12.3% | 16.7% | 12.4% | 11.2% | 19.0% | 10.2% | 15.7% | 13.3% | 8.3% | 10.3% | |
| 85 | 14.1% | 15.8% | 14.0% | 15.1% | 20.5% | 14.0% | 14.9% | 14.8% | 12.9% | |||
| 86 | 19.4% | 20.1% | 17.3% | 19.5% | 14.9% | 14.1% | 13.4% |
Groundball Rate
| SPIN | ||||||||||||
| VELOCITY | 1900 | 2000 | 2100 | 2200 | 2300 | 2400 | 2500 | 2600 | 2700 | 2800 | 2900 | 3000 |
| 68 | 42.9% | 20.0% | 38.9% | 30.4% | 22.2% | |||||||
| 69 | 75.0% | 25.0% | 40.0% | 45.5% | 26.7% | 42.1% | 75.0% | |||||
| 70 | 40.0% | 36.4% | 27.8% | 35.0% | 47.6% | 46.4% | 38.1% | |||||
| 71 | 25.0% | 37.5% | 41.7% | 51.5% | 28.0% | 44.7% | 32.0% | 35.3% | ||||
| 72 | 50.0% | 45.8% | 22.2% | 42.3% | 52.8% | 41.9% | 47.0% | 34.2% | 33.3% | 37.5% | ||
| 73 | 50.0% | 46.7% | 39.4% | 43.4% | 43.0% | 39.1% | 42.9% | 50.0% | 36.1% | 66.7% | 64.7% | 66.7% |
| 74 | 33.3% | 44.0% | 19.5% | 38.2% | 45.5% | 48.2% | 43.0% | 48.2% | 54.0% | 50.8% | 39.1% | 57.1% |
| 75 | 66.7% | 46.0% | 37.8% | 45.9% | 53.0% | 37.4% | 41.4% | 45.1% | 46.3% | 52.4% | 63.0% | 65.0% |
| 76 | 55.6% | 32.7% | 45.5% | 51.4% | 34.9% | 45.9% | 49.3% | 49.3% | 47.7% | 51.1% | 63.2% | 64.3% |
| 77 | 63.9% | 43.8% | 44.1% | 42.3% | 42.3% | 49.7% | 52.2% | 52.1% | 51.2% | 41.7% | 53.5% | 51.9% |
| 78 | 33.3% | 43.1% | 45.5% | 41.9% | 38.6% | 52.6% | 47.3% | 53.6% | 52.5% | 50.8% | 50.0% | 56.3% |
| 79 | 31.6% | 42.9% | 33.3% | 50.9% | 47.8% | 44.0% | 44.9% | 49.6% | 50.0% | 44.7% | 57.9% | 57.4% |
| 80 | 66.7% | 65.0% | 49.2% | 48.5% | 47.9% | 49.3% | 54.9% | 46.6% | 50.5% | 56.0% | 60.0% | 66.7% |
| 81 | 55.6% | 41.7% | 52.2% | 52.8% | 47.2% | 57.9% | 48.7% | 45.5% | 53.1% | 50.0% | 59.6% | 43.8% |
| 82 | 46.2% | 43.5% | 37.1% | 40.0% | 56.6% | 54.9% | 44.4% | 59.0% | 56.8% | 52.8% | 38.5% | |
| 83 | 55.6% | 37.0% | 43.2% | 38.2% | 45.7% | 57.7% | 47.5% | 60.9% | 45.8% | 56.0% | 69.2% | |
| 84 | 53.9% | 39.1% | 37.1% | 30.3% | 46.8% | 46.5% | 41.5% | 59.6% | 60.6% | 66.7% | 46.2% | |
| 85 | 50.0% | 52.6% | 63.6% | 42.2% | 42.2% | 37.8% | 57.1% | 56.0% | 53.9% | |||
| 86 | 44.4% | 36.4% | 38.1% | 52.4% | 50.0% | 61.5% | 66.7% | 60.0% |
Let me start with the second table before I get to the last disaster. Like with fastballs, a fast curve with the most spin gets the most swinging strike. This is not rocket science since the goal of every pitcher should be to throw as hard as possible with the most movement.
An important feature of this table happens with pitchers over 80 mph. The curves with the most spin at or under 80 mph max out their swinging strike rate around 12 percent. If a pitcher wants to move into the 15 percent or higher swinging-strike rates, they need to push for high and high curveball velocities.
Now, the next table is a mess. I graphed a few of the lines hoping for a pattern with no luck. I decided to simplify them down to just spin rate versus groundball rate and here are the results:
| SPIN RATE | GB% |
| 800 | 42.6 |
| 900 | 39.1 |
| 1000 | 40.6 |
| 1100 | 34.8 |
| 1200 | 42.7 |
| 1300 | 42.3 |
| 1400 | 47.1 |
| 1500 | 69.6 |
| 1600 | 55.3 |
| 1700 | 54.7 |
| 1800 | 41.4 |
| 1900 | 50.7 |
| 2000 | 43.8 |
| 2100 | 41.8 |
| 2200 | 44.3 |
| 2300 | 43.4 |
| 2400 | 47.5 |
| 2500 | 48.0 |
| 2600 | 47.5 |
| 2700 | 50.9 |
| 2800 | 50.8 |
| 2900 | 56.4 |
| 3000 | 57.0 |
| 3100 | 49.6 |
Now things get even more confusing. At the low spin rate end there is a groundball rate spike at 1,500 to 1,700 rpm, then it drops down to a low at 2100 rpm, and then ramps up again until it levels off around 2400 rpm. Usually, the more spin a curve has, the more sink it exhibits, and the more groundball it produces. I have no idea what is going on with the 1,500 to 1,700 jump. No pitcher averages in the range, so the pitches could be mistakes. Or maybe some slow curves messing with the data. Also, this may be where submarine pitchers work from. I am going to ask some people in the industry and look a little more into the results.
Ignoring the low rpm/groundball bump, pitchers get the best results with curves over 80 mph and 2,400 rpm. For a reference, here are the regulars with a curve meeting the two criteria ordered by velocity (min 100 curves thrown).
| PLAYER | CB VELOCITY | AVG SPIN | SwStr% | GB% | COUNT |
| Sam Dyson | 84.8 | 2862 | 11.3% | 30.0% | 151 |
| Lance McCullers | 84.6 | 2615 | 16.4% | 66.7% | 177 |
| Tommy Hunter | 84.4 | 2465 | 10.5% | 37.5% | 210 |
| Carlos Carrasco | 84.0 | 2502 | 13.6% | 62.8% | 426 |
| Yordano Ventura | 83.8 | 2578 | 9.2% | 57.6% | 1158 |
| Corey Kluber | 83.7 | 2490 | 16.0% | 44.4% | 870 |
| Ryan Pressly | 83.2 | 2888 | 9.4% | 36.4% | 235 |
| Bryan Mitchell | 83.0 | 2729 | 7.1% | 67.7% | 155 |
| Kevin Jepsen | 82.7 | 2433 | 7.4% | 55.9% | 458 |
| Stephen Strasburg | 82.1 | 2606 | 7.8% | 60.2% | 709 |
| Kelvin Herrera | 82.0 | 2655 | 8.9% | 52.0% | 101 |
| Gerrit Cole | 82.0 | 2480 | 9.2% | 34.0% | 349 |
| Will Harris | 81.7 | 2625 | 7.6% | 60.9% | 475 |
| Marcus Stroman | 81.7 | 2626 | 7.1% | 65.8% | 224 |
| Matt Bush | 81.6 | 2472 | 15.0% | 52.4% | 113 |
| Sonny Gray | 81.5 | 2690 | 7.1% | 46.7% | 702 |
| Buddy Boshers | 81.4 | 2432 | 14.8% | 57.1% | 128 |
| Carlos Torres | 81.3 | 2437 | 9.7% | 61.3% | 237 |
| Jake Arrieta | 81.2 | 2710 | 12.6% | 58.7% | 819 |
| Average | 10.6% | 53.1% | |||
| Median | 9.4% | 57.1% |
Looking at the curveball spin rate data, the results are the same as fastballs. Spin rate is a desired curveball pitch stat, but it needs to be paired with the pitch's velocity to start to value the pitch.
Conclusion
I didn't expect to find much will diving into pitch spin rates as I figured the results were baked into pre-existing pitch information. Both pitch types fall under the sage old advice that velocity and movement define a pitch. The more speed and spin on the pitch, the harder the pitch is to hit.
With four-seam fastballs, I did find spin rate helpful in explaining why 95 mph fastballs and pitches 5 mph slower perform similarly.
With curveballs, higher spin is helpful, but it is more important if the pitcher can throw his curve hard. Reported pitch spin is helpful, but it really needs to be put into context with velocity to understand how it helps the pitcher.
Spin rate by itself only tells half the story and sometimes not even that much.
