In the beginning of May, Andy Sonnanstine’s record was 4-1 and we noticed that his emergence this season may have been due at least in part to a change in his mechanics. Specifically, Sonnanstine was no longer using different arm angles, one of his trademarks.

Here is the plot we showed you earlier comparing Sonnastine’s release point in ’07 (left) to his release point in his first six starts of ’08 (right).

As you can see, the pitches on the right (’08) are much more clustered and more over the top.

Since we ran that post Sonny has struggled at times. We decided to go back and look again at Sonny’s Pitchf/x data. The results were surprising.

Here we have added the updated 2008 release point data to the right of the previous two clusters (2008a represents Sonnanstine’s first 6 starts of ’08; 2008b represents all of Sonnanstine’s ’08 starts).

A couple of points stand out…

  1. Sonnanstine is once again changing arm angles on his pitches, specifically his fastball and his splitter.
  2. The varying arm angles differ in ’08 as compared to ’07. The different release points appear to be spread more horizontally and he is not dropping his arm as he was in ’07.

Now let’s see how these changes have translated to The Duke’s stat lines…

The first (2007) and third (2008-starts 7-14) lines are when Sonnanstine was using different arm angles. The middle line represents when Sonnanstine was not varying his release point.

Once again, a couple of points stand out…

  • Sonnanstine’s stat lines are very similar when he is changing arm angles.
  • Sonnanstine clearly strikes out more batters when he changes arm angles, but he also gives up considerably more hits and his ERA is higher.
  • His walk rate appears consistent whether he is changing arm angles or not.
  • Sonny works deeper into games when he is not changing arm angles.

We must point out that we only have a small sample size of starts without changing arm angles (6 starts). Also, we don’t have a game-by-game breakdown, so we cannot be certain when Sonnanstine started varying his release point again, but we do know that it was after his first 6 starts of ’08.

Still, there appears to be a very clear trend: Andy Sonnanstine strikes out more batters when he changes arm angles, but he is a better overall pitcher when he does not.

Sonnanstine No Longer Changing Arm Angles [Rays Index]



  1. Possum Avenger says:

    nice analysis prof. Although somewhat counter intuitive. Why would changing arm angles lead to batters getting more hits? I can understand more strikeouts...

  2. DirtbagFan says:

    he's obviously not getting the location he wants when he changes arm angles...

  3. The Professor says:

    Sonny is a control pitcher. So his biggest weapon is accuracy and movement.

    Let's say he usually has a 7 curveball (scale 1-8). That is going to be hard to hit. Now if he throws that curveball from different arm angles, that adds to the difficulty. might even make it seem like an 8.

    BUT, once a pitcher changes his arm angle, he is changing his mechanics. It becomes much more difficult to throw a great curveball each time and keep mechanics consistent. So sometimes it might be a 7, but other times it might only be a 4 or 5 if he doesn't have perfect mechanics.

    think about throwing darts. the best way to stay consistent is to repeat the same delivery every time. all of the sudden try throwing a dart sidearm. Adds to the level of difficulty to be certain.

    Now this is all speculation which is why i didnt touch on it, but when Sonny is changing arm angles his pitches might sometimes be better or more difficult to pick up...but he might also sometimes lose a little bit on the pitches and they could more hittable if he doesnt get the same amount of break or he misses the corner and leaves it over the plate.

    in other words. if he keeps the same arm angle, he might throw a 7 all the time. when he changes arm angles, he might throw some 8s, some 7s and maybe some 4s and 5s. The 8s might add to the strikeout totals, but the 4s and 5s are adding to the hit totals.

    another factor might be the hitters. some hitters may struggle more with different arm angles. those batters might strikeout more. on the other hand some batters might not be bothered at all and if Sonny loses a lit break or location on a sidearm pitch, that pitch might be more hittable for some batters that arent affected by different arm angles


Leave a Comment