RVH - What the heck happened to Sean & Kodai this year?

 Now that we have a new pitching coach, here is a look into how the muscle pull injuries to Sean Manaea & Kodai Senga likely impacted their pitching mechanics, ultimately huge contributors to their subpar 2025 results. 

This breaks down what we saw this year and identifies the causal drivers for each pitcher. 

Hopefully, the team will be helping them focus on corrective actions this offseason and they recover going into 2026.

The “Swing Mechanics Equivalent” for Pitchers

If you think of a hitter’s swing mechanics exercise as isolating how efficiently kinetic energy flows from the ground up: sequencing, timing, torque, and barrel path; the pitching equivalent is analyzing the delivery’s kinetic chain and how efficiently energy transfers from the lower half → torso → arm → ball.

Let’s break this down systematically:

The Delivery Sequencing Exercise

Core diagnostic focus:

1. Ground Force Generation & Direction: How energy is produced by the drive leg and transmitted through the front side.

2. Hip–Shoulder Separation: The degree and timing of rotational separation (the pitcher’s version of “lag” in a swing).

3. Arm Path Efficiency: The shape and timing of the arm swing relative to trunk rotation — avoiding early/late launch.

4. Front-Side Bracing: How the lead leg stabilizes to convert linear momentum into rotational power.

5. Tempo & Rhythm: How seamlessly the motion flows; does the body “stack” energy or leak it in transitions?

Applications to Sean Manaea & Kodai Senga

1. Sean Manaea

Profile: LHP, long levers, low-effort look, traditionally more deception than raw velocity. 

Mechanical Pitching Diagnostic (Equivalent Swing View):

• His delivery resembles a power hitter who uses upper body torque more than lower-half explosiveness.

• Historically lacked strong ground-force generation — he drifts forward rather than driving off the rubber.

• Hip–shoulder separation is limited, so the arm has to generate more of the velocity (like a hitter muscling the bat).

• When synced (like 2023–24 Giants/Mets version), his shortened arm path and slightly more compact stride produced better timing, similar to tighter swing mechanics for more efficient bat path.

Mechanical Issue:

• Under-utilizes lower half; energy chain dominated by upper body.

• Limited hip–shoulder separation → poor energy transfer efficiency.

• Drifts forward rather than driving off the rubber.

Performance Translation:

Dimension	Effect
Velocity & “Life”	When sequencing leaks, his fastball flattens; loses late life. The perceived velocity drops because energy from the legs never fully transfers.
Command	Arm works harder to generate speed → inconsistent release point → more misses arm-side or elevated.
Hittability	Predictable plane + diminished deception = higher barrel rate. His “stuff” plays below raw velo readings.
Pitch Count	Because he must muscle pitches, fatigue sets in early. Missed locations mean longer at-bats and more foul balls → inefficient innings.
Game Depth	Typically caps at ~5 innings when inefficient; rarely carries top velocity and command past 70–80 pitches. When synced, efficiency improves dramatically, allowing 6–7 innings with lower perceived effort.

👉 In swing terms: Like a hitter muscling everything with arms—looks violent but produces inconsistent contact and tires quickly (aka Alvarez). 

Manaea – Lat Pull Impact

Normal Kinetic Profile:

• Upper-body–dominant delivery with limited lower-half contribution.

• Arm generates a disproportionate share of force.

• Sequencing already borderline — hips and shoulders rotate nearly together.

Injury Context:

• The lat is the primary link between the torso and the throwing arm.

• It stabilizes the scapula and helps accelerate and decelerate the arm through release.

• A pull/strain weakens the ability to generate or absorb rotational force.

When He Returned Midseason:

Chain Effect	Consequence
Reduced lat engagement → upper body protects the area	Slight drop in velocity and loss of extension; ball “floats” rather than carrying.
Compensation by triceps and shoulder capsule	Arm fatigue increases rapidly; command drifts high/arm side.
Reduced follow-through to guard the lat	Release point shortens; spin axis shifts → less late life.
Fatigue onset earlier	Efficiency collapses by the 3rd–4th inning. Pitch count inflates.

Macro Result:
– Effectiveness drops 10–15% (velo, movement, command).
– High probability of “dead arm” periods between starts.
– Until the lat fully restrengthens and the lower half takes more load, he can’t repeat long outings.

👉 Analogy: like a hitter with an oblique strain who can’t rotate through contact — they guide the bat instead of whipping it.

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2. Kodai Senga

Profile: RHP, athletic, explosive lower half, high-effort but whippy arm. “Ghost Fork” pitch dominates.

 Mechanical Pitching Diagnostic (Equivalent Swing View):

• He’s like a hitter with tremendous bat speed and natural “whip,” but prone to timing drift and energy leaks under stress.

• His kinetic chain is explosive but occasionally over-sequenced — hips fire early, torso over-rotates, forcing late arm catch-up (why command sometimes wavers).

• Elite arm–torso separation but can lose posture.

Mechanical Issue:

• Hyper-athletic but over-sequenced; hips fire early, arm plays catch-up.

• Tremendous hip–shoulder separation but occasional posture loss.

• “Whippy” arm path magnifies timing errors.

Performance Translation:

Dimension	Effect
Velocity & Movement	When timed right, elite — the “ghost fork” devastates hitters. But over-rotation or early hip fire causes late arm arrival → loss of velocity and inconsistent break.
Command	Timing drift = sporadic strike throwing. Walks climb (4+ BB/9) because arm arrives late, forcing pitches high or spiked.
Hittability	When behind in counts, he must rely on predictable fastballs. Hitters can sit on his heater, which rides but doesn’t always finish late.
Pitch Count	Frequent deep counts and walks inflate totals — 95+ pitches in 5 innings is common. Not pure fatigue; rather inefficient sequencing leading to poor economy of pitches.
Game Depth	Even with dominant stuff, it's hard to go 7+ innings because command issues elevate pitch count. Efficiency, not stamina, limits him.

👉 In swing terms: Like a hyper-power hitter with elite bat speed but inconsistent timing — either a bomb or a whiff, nothing in between.

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Senga – Right Hamstring Injury Impact

Normal Kinetic Profile:

• Power generated by dynamic lower half and elite hip–shoulder separation.

• Fast tempo, long stride, heavy reliance on push-off leg and lead-leg bracing.

Injury Context:

• The right hamstring (the push-off leg) initiates the chain: it loads, drives, and helps stabilize deceleration.

• A strained or recovering hamstring weakens drive mechanics and alters stride timing.

When He Returned Midseason:

Chain Effect	Consequence
Reduced drive force	Loss of velocity (1–3 mph) and diminished extension.
Shorter stride / altered landing angle	Timing drift; arm may arrive early or late relative to hips.
Guarded acceleration phase	Fastball plays flat; ghost fork loses depth.
Fatigue after 3–4 innings	Lower half stops generating ground force; upper body takes over → command inconsistency, pitch elevation.

Macro Result:
– Command volatility spikes (more walks).
– Harder to finish hitters; at-bat quality declines late in games.
– High pitch count per inning; stamina lags even when pain-free.
– Mechanical rhythm can take 4–6 starts to “re-sequence.”

👉 Analogy: like a slugger with a back-leg hamstring strain — they can’t load the rear hip fully, so timing and power vanish until confidence in the leg returns.

I hope the Mets can find a way to move Manaea and rehabilitate Senga going into 2026. They cannot open the season with 40% of their starting rotation with this type of injury / mechanics recovery status.