I am by no means a pitching expert but I did stay at a Holiday Inn Express last night so I am one at least for this article. If I could talk to every young pitcher who desires to pitch to learn a change-up. To me, it is the perfect pitch because it does not matter about the quality of the fastball as long as a pitcher can change speeds very effectively. It is what has allowed Jamie Moyer to pitch at least 10 years and it is what allowed Pedro Martinez come back and be effective for the Phillies and has made Johan Santana one of the best pitchers in the last 10 years. For those not familiar with the aspects of the change-up, here is a great video that briefly breaks it down:
While sitting here in the baseball conference this week, I have been toying around with numbers and trying to come up with some different angles to frame topics related to the Rays. Given my love of the change, it is only natural that James Shields is my favorite pitcher on the staff. I even make sure I tune in to watch his starts in Fenway knowing that his track record there is as good as George Custer’s at Little Big Horn. It is his best pitch and it means everything to what he does. How good is it? If you use the data at fangraphs.com and sort by pitch type leaders and sort by wCH, you will see that Shields was graded with the second best change-up in the American League in 2009 trailing only C.C. Sabathia. Shields works his best when he is throwing strikes early in the count and can get batters to chase his change which has tremendous fade to it.
If a pitcher cannot get that kind of fade on a change-up, they better have good separation between their fastball and change-up velocity. As the video above explained, the two pitches are thrown exactly the same and what makes Shields so effective when he is on is that he gets good velocity difference and movement on his change-up. Without the movement, the pitcher is relying upon the velocity difference to do the work so it goes without saying the further apart the velocity is on the two pitches, the more the hitter’s timing will be affected.
Pitchf/x data can help show how much pitches move and such, but I am by no means an expert on that and frankly, demonstrating that kind of stuff is above the tone I am trying to set for this blog. If you are interested in pitchf/x data, two of the best guys in the business for explaining it are Mike Fast and Harry Pavlidis as those are my two favorite guys to read and consult when I have questions in that arena. However, velocity data is easily available at fangraphs so we can easily get the fastball and change-up velocity of a group of pitchers to find out who has the biggest and smallest differences and try to find some correlation of success. For the purpose of this piece, I wanted to look for a correlation between the difference in velocity in a pitcher’s fastball and change-up and their ERA. I pulled the fastball velocities, the change-up velocities, and the ERAs of all pitchers who threw at least 100 innings in 2008 or 2009 and found 138 qualified pitchers which includes repeat performers in 2008 and 2009.
For that group, I found the average velocity difference was 8 miles an hour – which is exactly where Shields sits for his career. Overall, here is the data for the 138 pitchers:
differentials
| V-Diff | Mean ERA | Lowest | Highest | Count |
|---|---|---|---|---|
| 4-5 mph | 5.24 | 4.73 | 5.76 | 2 |
| 5-6 mph | 3.71 | 2.49 | 4.44 | 3 |
| 6-7 mph | 4.58 | 2.89 | 6.66 | 19 |
| 7-8 mph | 4.58 | 2.07 | 7.16 | 31 |
| 8-9 mph | 4.31 | 2.54 | 6.36 | 26 |
| 9-10 mph | 4.28 | 2.48 | 6.54 | 32 |
| 10-11 mph | 4.54 | 2.62 | 5.96 | 11 |
| 11-12 mph | 3.88 | 2.53 | 5.61 | 8 |
| 12-13 mph | 4.38 | 3.45 | 4.89 | 3 |
| 13+ mph | 3.80 | 3.49 | 4.03 | 3 |
| < 10 mph | 4.42 | 2.07 | 7.16 | 113 |
| > 10 mph | 4.22 | 2.53 | 5.96 | 25 |
When looking for a correlation for this from this table, there just is not much to find here. Overall, the correlation coefficient for this was only -0.11 which shows a very weak correlation (click thumbnail below for full-size chart).
The relation shows up at the 9-10 mph difference as the highest ERA continues to improve as the velocity difference increases. However, pitchers that do throw at least 90 and have changeups 8mph or slower have stronger ERA’s than the soft-tossers. The average ERA of the 138 pitchers improves with each added criteria:
- Average ERA of pitchers throwing under 90 mph = 4.69
- Average ERA of pitchers throwing under 90 mph but have at least 8mph difference between fastball and change-up = 4.45
- Average ERA of pitchers throwing at least 90 – 4.40
- Average ERA of pitchers throwing at least 90 and have at least 8mph difference between fastball and change-up = 4.22
Luckily for us Rays fans, Shields does throw at least 90mph and not only has good action on his change-up, but also has the separation that helps, at least somewhat, pitchers get toward a better ERA. Obviously, many more factors go into ERA such as hit rate, strand rate, home run to fly ball rate, and the like but velocity and changing speeds plays a part in all of those things and those are two things that Shields is still doing very well right now and something David Price showed signs of doing as the season went on and he gained more confidence in his change-up.
