Jakob Marsee
400 PA · sample confidence ×1 · full player page
1 · What changed (2026 vs 2025)
Moving against him
SLG−.188
xSLG−.133
AVG−.098
wOBA−.080
xBA−.058
Sweet-spot rate−11.4%
xwOBA−.048
Hard-hit rate−7.9%
Barrel rate−4.8%
Avg exit velocity−2.2 mph
Squared-up rate−3.8%
Chase rate+3.5%
In his favor / neutral
Avg launch angle+7.5°
Ground-ball rate−6.2%
Zone contact+4.4%
Walk rate+3.4%
Opposite-field rate+3.9%
2 · Why — ranked hypotheses
1. Plate-discipline erosion — expanding the zone
46%Causal path: Swing decisions → Contact rate → Actual outcomes
- • Chase rate +3.5% vs last season
- • Zone contact +4.4% vs last season(in-zone contact intact isolates the problem to decisions)
Against / absent: Walk rate +3.4% vs last season · Strikeout rate +1.8% vs last season
2. Timing issue — late to the ball
39%Causal path: Swing/pitch mechanics → Swing length → Batted-ball profile → Expected outcomes
- • Opposite-field rate +3.9% vs last season
- • Avg exit velocity −2.2 mph vs last season
- • Bat speed +0.0 mph vs last season(bat speed intact rules out strength loss)
Against / absent: Ground-ball rate −6.2% vs last season · Whiff rate −0.5% vs last season · Late timing rate +0.0% vs last season
Mechanics themselves are unobserved in public data; inferred from the batted-ball fingerprint.
Unexplained / unobserved causes: 15% — confidence is deliberately capped; public data cannot see every layer.
3 · What the coach does tomorrow
Pitch-recognition sessions (occluded video or spin-recognition reps)
Standard training for chase-rate problems; targets the decision, not the swing.
Controlled-take rounds in BP (swing only at middle-middle)
Classic zone-discipline reset; rebuilds the take muscle without mechanical interference.
Post-game zone chart review with the player
Show the chase locations from the data; awareness precedes adjustment.
Actions follow the top hypothesis; if video review rejects it, fall to the next.
Data gaps
- • Biomechanics (Hawkeye), TrackMan, and Blast Motion are team-internal — the mechanics layer is inferred from its downstream fingerprint, never observed.