modern techniques for evaluating hitting alan m. nathan university of illinois batted ball analysis...

Modern Techniques for Evaluating Hitting

Alan M. NathanUniversity of Illinois

• Batted ball analysis– Initial speed and angles– Landing point and hang time

• Swing analysis– Bat speed– Swing plane– Timing– “squaring up” 1

Introductory Remarks

• Tradition techniques are “outcome-based”–BA, SLG, OPS, BABIP, …

• Modern techniques are “process-based”, independent of outcome–What constitutes a well-hit ball?–What constitutes a good swing?

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Tools for Modern Technique

• Baseball Info Solutions (BIS)–Batted ball landing point and hang time

• Hitf/x– Initial batted ball speed and angles

• TrackMan or Fieldf/x–All of the above (i.e., full trajectory)

• Physics–Relating batted ball to swing parameters

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Example: HITf/x Analysis

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See Mike Fast, BPro, Nov. 16 & 22, 2011

• ~50% of balls hit with BBS90 mph are safe hits, regardless of VLA

• ~37% of balls hit with BBS 90 mph and 250≤VLA≤350 are HR

BABIP

HR

What Constitutes “Good Contact”? Hitf/x from April 2009

BABIP

HR

What Constitutes “Good Contact”? Hitf/x from April 2009

• ~80% of balls hit with 100≤VLA≤150 are safe hits, regardless of BBS

• ~68% of balls hit with 100≤VLA≤250 and 60≤BBS≤80 mph are safe hits

Potential of These Data

• Quantify “good contact” (GC)• Establish outcome-inpependent metrics for

hitting based on GC• Investigate relationship between GC and

pitching metrics• Small sample size and sustainability• Potential even greater if landing point &

hang time are known– Ben Jedlovic’s talk at 2013 SABR Analytics

Example

Divide BBS-VLA space into rectangles• For each rectangle, assign a value

based on some useful metric–e.g., BA, SLG, Linear Weights, …

• For any hitter, weighted average can be computed to arrive at overall metric

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Landing Point/Hang Time(image courtesy of BIS)

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Small horiz speed

Large horiz speed

Ex: Two MLB Hitters(images courtesy of BIS)

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Batter #1 Batter #2

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tof:R:bbs

bbs:vla:R

Comparing the two methods using TrackMan dataBBS

R

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tof:R:bbs

bbs:vla:R

BBS

R

Comparing the two methods using TrackMan data

(bbs,vla) (tof,R)?

13Considerable variation of R for fixed bbs,vla.

All stadiums

covered stadiums

Why does initial velocity not determine landing point

accurately?• Variation in air density

– Easy to control• Variation in wind

– Not so easy to control, except for covered• Variation in spin

– More in a mintue• Variation in surface properties of ball

– A topic of intense interest (to me!)14

Related question: Is greater “carry” a skill?

• In particular, is ability to put backspin on ball a skill?

• With both initial velocity vector and landing point/hang time, we can address this question for individual batters

• Related to swing parameters

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New Research Project

• Can batted ball data determine swing parameters?

• A very challenging physics problem• In this talk I will

– State the problem– Discuss progress in solving

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Bat Swing Parameters• Bat speed determined by pitch and

batted ball speed• Fan: timing of swing• Tilt: to swing plane• Offset: “squaring up”

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fan

tiltE = offset

Current State

• Bat swing parameters can predict batted ball parameters.– fan+tilt+offset HLA+VLA+spin axis

• Can batted ball parameters determine bat swing parameters?

Simple Example:Straight Pitch, RHH, Tilt=00

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E=0”

E=-1”

E=0

E=+1”

Fan=00 Fan=-150Fan=150

Simple Example:Straight Pitch, RHH, Tilt=450

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E=-1”

E=0

E=+1”

Fan=00

Fan=-150

Fan=150

A Brief Aside:Spin of a Batted Baseball

2000 fps120 mph

friction

normal force

Fly balls break toward foul line

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450-450

00

LF

RF

Effect of tilt on spin axis

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Tilt Balls hit to CF slice

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RHH

LHH

Current State of Affairs

Spin axis might be able to determine tilt angle

Spin axis can be determined from trajectory

hang time backspin

lateral deflectionsidespin

spin axis ~ tan-1(sidespin/backspin)

Work still in progress but It looks promising that

HLA+VLA+spin axis fan+tilt+offset25

Summary/Outlook

• We have some new tools for evaluating batting based on process rather than outcome

• Determining swing parameters from batted ball data looks promising but still a work in progress

• Progress on both fronts would benefit greatly from existing data that are not readily available

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