基礎知識

xFIP(Expected Fielding Independent Pitching)



概要

被本塁打による揺らぎを排除したFIP。統計的な研究により、投手の外野フライに対する本塁打の割合は長期的には一定の割合に収束するとされる。この性質に基づき、外野フライに一定の割合の本塁打を見込んでFIPを計算するのがxFIPである。絶対数が少なく揺らぎが大きい被本塁打の影響を排除して投手の実力を評価することができる。


計算式

xFIP=(13×(本塁打÷(外野フライ+本塁打))×外野フライ+3×(与四球-故意四球+与死球)-2×奪三振)÷投球回+定数

※定数=リーグ全体の{失点率-(13×(本塁打÷(外野フライ+本塁打))×外野フライ+3×(与四球-故意四球+与死球)-2×奪三振)÷投球回}


背景

xFIPの元となるFIPは、奪三振・与四死球・被本塁打に得点価値の比重を掛けて守備から独立した防御率を計算する指標である。投手の実績の評価としてはFIPは成立した指標であるが、被本塁打は失点への影響が強いため大きな比重がかかり、また被本塁打は奪三振・与四死球・被本塁打という守備から独立した項目の中では絶対数が少なく運によって揺らぎやすい項目である。このため短期の投手のFIPは被本塁打数の揺らぎによって大きく左右されることとなり、投手の能力を反映しない可能性がある。


xFIPは上記の問題に対処するため、FIPの計算の被本塁打の部分に修正を加える。すなわちFIPのように被本塁打数に直接係数を掛けるのではなく、その投手が打たせたフライの数を計算の対象とし、フライに対して平均的に見込まれる本塁打の割合から「打たせたフライの数に対して一般的にあるべき被本塁打数」を計算してその数字に係数を掛ける形でFIPを計算する。


このような計算を行うことによりxFIPの意味は「フライに対する本塁打の比率がリーグ平均と等しかったと仮定した場合のFIP」となる。このためxFIPは単に守備から独立した項目に基づく実績を示すFIPとは異なり「あるべき成績」や予測を示す性格の指標である。


計算式の導出としては、投手の責任範囲を奪三振・与四死球・被本塁打の3項目と定め、LWTSに基づき投球回あたりの失点の多さを評価する式を構築する。



シーズンのFIPランキングはこちらから



指標一覧

指標右側のタグは"Leaders" 内のテーブルにリンクされています。Batting > Standard と表示されていた場合、"Leaders"メニュー内の"Batting""Standard" のテーブルにリンクされています。
1B
One-base Hit
Batting > Standard
2B
Two-base Hit
Batting > Standard
3B
Three-base Hit
Batting > Standard
AVG
Batting Average
Batting > Standard
AVG
Batting Average
Batting > Advanced
AVG
hits allowed average
Pitching > Advanced
BABIP
Batting Average on Balls In Play
Batting > Advanced
BB
Base on Ball
Batting > Standard
BB
walks and given
Pitching > Standard
BB/K
walk-to-strikeout ratio
Batting > Advanced
BUH%
bunt hit percentage
Batting > Batted Ball
CG
complete game
Pitching > Standard
CS
Caught Stealing
Batting > Standard
CS
caught stealing
Pitching > Standard
ERA
earned run average
Pitching > Standard
exLI
Average Leverage Index when exiting the game
Pitching > Win Probability
FB%
fly ball percentage
Batting > Batted Ball
FB%
fly ball percentage
Pitching > Batted Ball
FT%
Two Seam Fastball percentage
Batting > Pitch Type
FT%
Two Seam Fastball percentage
Pitching > Pitch Type
FTv
Two Seam Fastball velocity
Batting > Pitch Type
FTv
Two Seam Fastball velocity
Pitching > Pitch Type
GB%
ground ball percentage
Batting > Batted Ball
GB%
ground ball percentage
Pitching > Batted Ball
GB/FB
ground ball to fly ball ratio
Batting > Batted Ball
GB/FB
ground ball to fly ball ratio
Pitching > Batted Ball
GBOut%
ground ball out percentage
Batting > Batted Ball
GDP
Grounded into Double Play
Batting > Standard
gmLI
Average Leverage Index when entering the game
Pitching > Win Probability
HBP
Hit By Pitch
Batting > Standard
HBP
hit by pitch
Pitching > Standard
HR
home runs allowed
Pitching > Standard
IBB
Intentional Base on Ball
Batting > Standard
IBB
intentional base on balls
Pitching > Standard
IFFB%
infield fly ball percentage
Batting > Batted Ball
IFFB%
infield fly ball percentage
Pitching > Batted Ball
IFH%
infield hit percentage
Batting > Batted Ball
inLI
Average Leverage Index at the start of the inning
Pitching > Win Probability
IP
innings pitched
Pitching > Standard
K%
strikeouts rate
Batting > Advanced
K-BB%
strikeout-walk rate differential
Pitching > Advanced
LD%
line drive percentage
Batting > Batted Ball
LD%
line drive percentage
Pitching > Batted Ball
OBP
On-Base Percentage
Batting > Advanced
O-Contact%
Z-Contact%
Contact%
contact percentage
Batting > Plate Discipline
O-Contact%
Z-Contact%
Contact%
contact percentage
Pitching > Plate Discipline
OFOut%
outfield fly out percentage
Batting > Batted Ball
OPS
On-base Plus Slugging percentage
Batting > Advanced
O-Swing%
Z-Swing%
Swing%
SwStr%
swing percentage
Batting > Plate Discipline
O-Swing%
Z-Swing%
Swing%
SwStr%
swing percentage
Pitching > Plate Discipline
PA
Plate Appearance
Batting > Standard
PH
Pinch Hit Opportunities
Batting > Win Probability
PhLI
Average Leverage Index while Pinch Hitting
Batting > Win Probability
pLI
Player Average Leverage Index
Batting > Win Probability
pLI
Player Average Leverage Index
Pitching > Win Probability
Pull%
Cent%
Oppo%
batted ball direction
Batting > Batted Ball
Pull%
Cent%
Oppo%
batted ball direction
Pitching > Batted Ball
R
runs allowed
Pitching > Standard
RBI
Runs Batted In
Batting > Standard
RE24
Run Above Average based on the 24 Base/Out States
Batting > Win Probability
RE24
Run Above Average based on the 24 Base/Out States
Pitching > Win Probability
REW
Wins Above Average based on the 24 Base/Out States
Batting > Win Probability
REW
Wins Above Average based on the 24 Base/Out States
Pitching > Win Probability
SB
Steal a Base
Batting > Standard
SB
steal a base
Pitching > Standard
SF
Sacrifice Fly
Batting > Standard
SH
Sacrifice Hit
Batting > Standard
SLG
Slugging percentage
Batting > Advanced
SO
Strike Out
Batting > Standard
Soft%
Mid%
Hard%
quality of contact stats
Batting > Batted Ball
Soft%
Mid%
Hard%
quality of contact stats
Pitching > Batted Ball
TBF
total batters faced
Pitching > Standard
WAR
wins above replacement
Batting > Value
WAR
WAR
wins above replacement
Pitching > Value
WAR
wCB/C
Curveball runs above average per 100 pitches
Batting > Pitch Value
wCB/C
Curveball runs above average per 100 pitches
Pitching > Pitch Value
wCH/C
Changeup runs above average per 100 pitches
Pitching > Pitch Value
wCT/C
Cutter runs above average per 100 pitches
Pitching > Pitch Value
wFA/C
Fastball runs above average per 100 pitches
Batting > Pitch Value
wFA/C
Fastball runs above average per 100 pitches
Pitching > Pitch Value
wFT
Two Seam Fastball runs above average
Batting > Pitch Value
wFT
Two Seam Fastball runs above average
Pitching > Pitch Value
wFT/C
Two Seam Fastball runs above average per 100 pitches
Batting > Pitch Value
wFT/C
Two Seam Fastball runs above average per 100 pitches
Pitching > Pitch Value
WP
wild pitch
Pitching > Standard
wSB
weighted Stolen Base runs
Batting > Advanced
wSF/C
Splitter runs above average per 100 pitches
Batting > Pitch Value
wSF/C
Splitter runs above average per 100 pitches
Pitching > Pitch Value
wSI/C
Sinker runs above average per 100 pitches
Batting > Pitch Value
wSI/C
Sinker runs above average per 100 pitches
Pitching > Pitch Value
wSL/C
Slider runs above average per 100 pitches
Batting > Pitch Value
wSL/C
Slider runs above average per 100 pitches
Pitching > Pitch Value
wSP/C
Special runs above average per 100 pitches
Batting > Pitch Value
wSP/C
Special runs above average per 100 pitches
Pitching > Pitch Value
Zone%
F-Strike%
pitches in the strike zone percentage
Batting > Plate Discipline
Zone%
F-Strike%
pitches in the strike zone percentage
Pitching > Plate Discipline
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