Athlete Highlight: Hunter College HS Junior Justin Lin up from T84 mph to T91 mph

Justin Lin (Class of 2025) is a veteran of the RPP Fam, having joined us in 2021. Needless to say, the gains have been significant. Last fall, Justin came back at 6’1”, 187 lbs. topping out at 84 mph (6/23 PG). After a couple of unfortunate injuries last year, he got after it this off-season and the results are showing. He is now T91 mph and sitting upper 88-90 mph. His fastball velo is up 6-7 mph.  In addition, he has developed one of the best pitching arsenals we have seen at RPP from a high school level player (Trackman results available).

How did he do it?

Justin’s off-season started unconventional to many others. After rehabbing two different injuries, we were able to do a complete assessment on Justin. The assessment included a movement screen, strength and power testing, and a mechanical breakdown of his delivery, combining both motion capture and video analysis.

Every pitcher wants to throw harder and getting them to do so is best achieved by targeting each athlete’s lowest hanging fruit and improving movement. As for Justin, we identified a few aspects of his assessment that had room for improvement. Let’s dive into some specifics.

Movement Screen / Mobility

The mobility portion of the assessment is crucial in not only analyzing an athlete’s movement strategies, but detecting mobility restraints that may be limiting him from getting into more efficient positions on the mound. In many cases, some of the issues that are presented in this portion of the assessment will be evident when we are evaluating the pitcher’s mechanics in the latter part of the assessment. In Justin’s case, three topics stood out:

    • Core Control: One’s ability to maintain a strong core, both in the gym and on the mound, will lead to the athlete putting themselves in better positions. In Justin’s case, his core control was lacking due to an anterior pelvic tilt creating excess lumbar spine extension. It is important to create stiffness in the core because energy is stored and created proximally and then transferred to the distal parts of the body. A weak core can lead to an athlete’s ribs flaring and losing their trunk stack as they work down the mound.
    • Shoulder IR: The internal rotation of the glenohumeral joint is mostly responsible for how well a pitcher can pronate/decelerate their arm after release. A lack of internal rotation will put the pitcher in a position where his shoulder is slamming shut which will put extra unnecessary pressure on the anterior shoulder and posterior elbow.
    • Lower Half Strength / Stability: One of Justin’s big players was the lack of stability in his lower half. When assessing this, we pinpointed inefficient movement strategies with his hips in all planes of motion (see below). Making sure we have a strong, stable base is crucial for not only force production and using the ground to our advantage but reducing injury / setbacks as well.

Body Composition

At 6’2”, 187 lbs. and 14% body fat, Justin entered the gym last fall as a well put together athlete. After getting after it in the weight room and a continued focus on nutrition, Justin is now 192 lbs. and 11% Body Fat at the end of our offseason training. Losing “body fat” and adding “lean muscle mass” has made him overall a better mover and athlete.

Often times with athletes at this age, making sure they are aware of what they need to work on is just as important as doing it. Becoming an even leaner and stronger version of himself was something we put an emphasis on, and it has paid off.

Strength and Power

After completion of the movement screening, we then moved on to our strength and power testing. Strength and power testing gives us more information about the type of athlete we are dealing with and higher gains in these two categories helps create a higher velocity ceiling, with less force having to be produced by the arm. This is especially true with the huge increase in his ability to decelerate his lead leg (RSI).

We were able to measure Justin’s initial Strength and Power numbers from November and compare them side-by-side with his numbers from the beginning of March. Below are his metrics:

Lower Half Power:

    • 13% increase in his CMJ Jump
    • 9% increase in his Squat Jump
    • 23% increase in his Lead Leg RSI


    • 12% increase in his Deadlift
    • 5% increase in his Bench Press
    • 10% increase in his Single Leg Squat

Final Strength and Power Testing Results

Striving to improve his power while using his strength-shortening cycle as well as becoming a stronger athlete has in turn led to Justin improving his body composition and becoming a more explosive athlete.

Mechanical Delivery          

The final part of Justin’s evaluation was his mechanical breakdown, which we assessed through Motion Capture and Video Analysis. Motion capture data is great with being able to pick up things that are difficult to see with the naked eye, such as angular velocities and thus supplying us with greater insight as to what is really happening throughout his delivery.

Things he did well:

    • Pelvic / Glute Engagement / Timing: By holding tension in the ground as long as possible, we can effectively engage our pelvis/glute. This is where energy and force are created in the pitching delivery. Justin doing this well allows for him to use the ground reaction force to his advantage and have said force be sent up his kinetic chain all the way through ball release.
    • Trunk Rotation: Justin does a great job at keeping his torso closed as he drifts down the mound. By keeping his torso closed, he is able to use his Strength Shortening Cycle and stretch the coil to the point when he goes to deliver the ball, he has so much kinetic energy built up that he is able to explode into ball release. He is also putting his body in a much better position to accept force with his front leg and effectively block with the lead leg.
    • Weight Shift (Drifting): The purpose of drifting is to initiate the athlete’s movement down the mound in order to apply force in a linear direction once the athlete starts to work down the mound. Justin does a great job of using the slope to his advantage, allowing him to put his body in an elite position to move effectively and efficiently.

Things that needed work:

    • Early Hip Rotation: Due to the looseness of his hips, Justin exhibits an early lead leg action in terms of his pelvis rotating. We want our hips to rotate in sequence with the rest of our body so we can put our lead foot in the most optimal position to decelerate and optimize the timing of our hip-shoulder separation. Justin’s front hip rotated early, which can lead to these inefficient movement patterns.
    • Shoulder ER at Foot Plant: When we get to weight bearing foot plant, we ideally want to see the arm between 40-75 degrees of external rotation. Justin was what we consider a “Late Riser” which means his arm is flipping up slightly late when he gets his front foot down.
    • Trunk Stack at Foot Plant: This is defined as the pitcher’s ability to keep his pelvis and upper body “stacked” from the beginning of the linear move all the way into front foot strike. Failure to maintain the trunk stack will make it difficult to achieve efficient rotation and forward trunk flexion later in the delivery. Justin’s trunk issues were due to his excess lumbar extension which led to a lack of core control. This would come into play when he was transitioning from leg lift into foot plant, and you would see his ribs begin to flare (extend) and posture become arched due to a lack of anterior core strength and stability.

How we addressed his movement deficiencies?

Following the completion of the mechanical assessment, and once mobility issues began to clean up, we generally prescribe throwing correctives in addition to his strength work in the gym. The intent here is to help improve overall movement patterns on the mound. Below are the drills we gave Justin to help improve these deficiencies:

Standing Go Call: Focuses on the dissociation of the torso from the pelvis while the pelvis is in a locked position. Maintaining a loose arm path throughout.

Figure 8 Rocker: Used to help athletes feel a more loose/relaxed arm and shoulder to eliminate muscling up the arm and putting it in a more efficient position to deliver the ball while putting our lower half in a position to rotate aggressively.

Rhythmic Breaks: Focuses on staying connected to the ground during the forward move. Simulates the pitching delivery until foot plant and puts the arm and pelvis in an elite position.

Step Behind w/ Constraint: Used to improve timing of the pelvis, trunk stack, and overall kinematic sequencing while generating force with the back leg. The constraint used was a cone/hurdle to encourage getting the front foot down fast to prevent early hip rotation.

Pitch Design

One of the things that makes Justin elite is his pitch arsenal that we have developed with him here at RPP. He has a 4-pitch mix, including a 4-Seam Fastball, Sinker, Splitter, and Slider. Below are the metrics on Justin’s pitches:

    • 4SFB: 88-89 T91mph, 2300 rpm, 17’ IVB, 8.4’ HB, Stuff+ of 77
    • SNK: 85-87 mph, 2000 rpm, 8.6’ IVB, 15.4’ HB, 2:00 Tilt, Stuff+ of 101
    • SPL: 77-79 mph, 650 rpm, -4.6’ IVB, 8.4’ HB, 3:30 Tilt, Stuff+ of 147
    • SL: 79-81 mph, 2300 rpm, 0’ IVB, -7.5’ HB, 0.8° VRA, Stuff+ of 80

Our Stuff+ model is built on MLB averages, so it is to be taken with a grain of salt when analyzing a high school pitcher up against some of the best in baseball. In our model, a grade of 100 would be considered big league average.

The main contributor to some of Justin’s lower grades (FB and SL) is the velocity. Velocity is one of the more weighted variables in our model so his fastball being 3 mph and slider being 4 mph slower than MLB average is what hurts him here. But in terms of movement, spin, and release metrics, Justin hangs in there with some of the best arms in baseball and as he gets older and the velocity increases, his Stuff+ grade will as well.

As a 17-year-old athlete, to have MLB caliber pitches is a great way to separate yourself from the rest of your class. Justin’s SNK and SPL Stuff+ grades are both above MLB average. So where can he improve?

In regard to the SPL, a grade of 147 is 47% above league average. It doesn’t get much better than that. To put things in perspective, which is right up there with Devin Williams (Stuff+ of 159) who is regarded to have the best CH/SPL in all of baseball.

Lastly is Justin’s SNK. While he sports a grade of 101 (1% above league average), there is a lot of room for improvement. While his spin and release metrics are solid, his breaks need improvement. As stated above, Justin’s tilt of his SNK is 2:00. The closer we can get his wrist position to 3:00, the more vertical break he can kill and the more horizontal break he can add.

Justin’s pitching arsenal is one of the best at RPP and it’s just another one of the reasons he is on track to play at higher levels.

Summary Results

Justin has worked his tail off during the past couple of years. He heads into his junior year summer touching 91 mph, with a 7 mph gain on his heater, improved mechanics, and an elite pitch repertoire.

With his improved mechanics and arsenal, Justin has the potential to showcase himself in front of the country’s best and he is certainly someone to keep your eye on over the coming years.

Best of luck this season Justin!

By Matthew Hartshorn (Pitching Coordinator)


You live too far to train with us in-house at RPP? You can now train with us on a REMOTE basis.

You can also reach us through our various platforms or simply click below to schedule a phone call.

If you’re interested in receiving our blogs, please enter your email address below!