Tommy Shirley Pitching Mechanics

Few prospect have created the buzz that Tommy Shirley has this year. He's gone from a semi-forgotten left-hander with a track record rattled with injuries and unknowns to a AAA starter following a dominant stint in AA. His stats have been screaming prospect while scouting reports just weren't as inspiring. Never the less, I was quite excited to catch a start from him a week ago today in Nashville, TN.

Everyone wants to know about stuff, so I'll get that out of the way first. I talked to the ONE scout there which is a little less than usual. Incidentally, it wasn't the Miami Marlins scout that is usually there to cover the PCL. Ironic since it was the Marlins whom the Astros traded a AAA player a week later to.

He told me that Shirley was 87-92 on his fastball. Has some tail and sink to it. He runs in on the hands to both handed hitters. He throws a curve with good break that can be 12-6 at times and 1-7 at others. He also changes speeds with a change up.

I had several first impressions of Shirley's mechanics.

1. He starts his delivery with his hands high over his head.

2. It's quite funky with a very quick and deliberate windup But, then slows down during his leg lift before exploding to the plate.

3. He doesn't have a firm front side (a good thing), and whips his body around (not such a good thing)

4. His delivery is very difficult on left-handed hitters and hides it really well to them. However, he shows the ball to right-handed hitters quite visibly on the back side of his windup.

Kinematic Measurements

Max Knee Height: 52 inches (67% of height)

Stride Length: 58 inches (75% of height)

Shoulder Abduction at Foot Strike: 105 degrees

Knee Flexion at Foot Strike: 133 degrees

Max External Rotation: 174 degrees

Hip Flexion at Release Point: 78 degrees

It's quite an interesting delivery. There are two measurements that are outside of the norms for "Elite Pitchers" based on the research from the American Sports Medicine Institute. Those are his arm is slightly more abducted which adds stress to his elbow and his hip is more flexed than it should be at his release point.

The shoulder abduction is really just a few degrees. It should be between 80-100 degrees. It's at 105 degrees. By raising his shoulder that high, he increases the distance his elbow has to travel and increases stress on the UCL. He also goes into the "horizontal W" where his elbow extends back into horizontal abduction of the shoulder which also increases the distance of the elbow travels but also increases shoulder stress.

The hip flexion is also a concern. Too much hip flexion can create a block to the torso during deceleration. Although, Shirley can go through a full deceleration phase with his trunk since he doesn't have a firm front side and can rotate around his plant leg.

The issue with that is that he accomplishes that by getting very rotational in his delivery by having poor posture through his delivery and swinging his plant leg to his foot strike. That rotational aspect can really cause issues in finding a consistent release point and establishing good control, something he's had trouble with in the past. He showed significant improvement in AA this season based on his walk rate. However, that hasn't been the case in AAA as he has more walks (9) than strikeouts (8) in his 20 innings of work.

I will give him props though, he started using Jaeger J-Bands this off-season for his workouts and reportedly that has really helped him.

Overall, I think his mechanics will be a limiting factor to his future role. I think few expect him to be a starter, and I am surely with the majority in seeing him as a reliever. I just don't see enough pure and consistent stuff to really play against RHHs to be a starter as I think his mechanics will allow for good enough control and command moving forward.