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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?
2
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
3
Example: HITf/x Analysis
4
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
8
Landing Point/Hang Time(image courtesy of BIS)
9
Small horiz speed
Large horiz speed
Ex: Two MLB Hitters(images courtesy of BIS)
10
Batter #1 Batter #2
11
tof:R:bbs
bbs:vla:R
Comparing the two methods using TrackMan dataBBS
R
12
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
15
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
16
Bat Swing Parameters• Bat speed determined by pitch and
batted ball speed• Fan: timing of swing• Tilt: to swing plane• Offset: “squaring up”
17
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
19
E=0”
E=-1”
E=0
E=+1”
Fan=00 Fan=-150Fan=150
Simple Example:Straight Pitch, RHH, Tilt=450
20
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
22
450-450
00
LF
RF
Effect of tilt on spin axis
23
Tilt Balls hit to CF slice
24
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
26