What’s wrong with the OPS analysis in baseball

Keith R. Thompson,

January 2008

In recent years the OPS ratio in Baseball (On-Base Plus Slugging Percentage) has gained widespread acceptable as an analytical tool in evaluating a player’s skills. The argument is that it effectively captures the ability of a player to both get on base and hit for power – two very valuable hitting skills. The alleged value of the tool is also compounded by the fact that an OPS of .900 or higher typically puts the hitter in the upper echelon of offensive ability, with the league leaders in OPS generally scoring at or near the 1.000 mark.

The following table shows the overall MLB leaders in OPS during the 2007 season:

Rank

Player

Team

Runs

RBI

BA

OBP

SLG

OPS

1

Alex Rodriguez

NYY

143

156

0.314

0.422

0.645

1.067

2

David Ortiz

BOS

116

117

0.332

0.445

0.621

1.066

3

Carlos Pena

TAM

99

121

0.282

0.411

0.627

1.037

4

Chipper Jones

ATL

108

102

0.337

0.425

0.604

1.029

5

Magglio Ordonez

DET

117

139

0.363

0.434

0.595

1.029

6

Prince Fielder

MIL

109

119

0.288

0.395

0.618

1.013

7

Matt Holliday

COL

120

137

0.340

0.405

0.607

1.012

8

Albert Pujols

STL

99

103

0.327

0.429

0.568

0.997

9

Chase Utley

PHI

104

103

0.332

0.410

0.566

0.976

10

Ryan Howard

PHI

94

136

0.268

0.392

0.584

0.976

The result shows that the OPS measure (while a good indicator of hitting and slugging) does not correlate well with other success metrics such as runs scored and RBIs. In 2007 Alex Rodriguez led the majors in OPS, RBIs and Runs Scored. However, among the rest of the players within the OPS ton ten only two others (Magglio Ordonez and Matt Holliday) were also in the top ten in RBIs and Runs Scored. In fact, the player with the second-highest ranked OPS – David Ortiz – was only ranked 11th and 10th in RBIs and Runs Scored respectively. And Carlos Pena, with the third-highest OPS score was only 31st in Runs Scored in the majors in 2007.

In case one was wondering whether the results of 2007 were an aberration, consider these facts for the top ten OPS leaders during the first decade of the 20th century.

2006 Season

 

Rank

Player

Team

Runs

RBI

BA

OBP

SLG

OPS

 

1

Albert Pujols

STL

119

137

0.331

0.431

0.671

1.102

 

2

Travis Hafner

CLE

100

117

0.308

0.439

0.659

1.097

 

3

Ryan Howard

PHI

104

149

0.313

0.425

0.659

1.084

 

4

Manny Ramirez

BOS

79

102

0.321

0.439

0.619

1.058

 

5

David Ortiz

BOS

115

137

0.287

0.413

0.636

1.049

 

6

Lance Berkman

HOU

95

136

0.315

0.420

0.621

1.041

 

7

Jim Thome

CHW

108

109

0.288

0.416

0.598

1.014

 

8

Jermaine Dye

CHW

103

120

0.315

0.385

0.622

1.006

 

9

Miguel Cabrera

FLA

112

114

0.339

0.430

0.568

0.998

 

10

Carlos Beltran

NYM

127

116

0.275

0.388

0.594

0.982

 

2005 Season

 

Rank

PLAYER

TEAM

Runs

RBI

BA

OBP

SLG

OPS

 

1

Derrek Lee

CHC

120

107

0.335

0.418

0.662

1.080

 

2

Albert Pujols

STL

129

117

0.330

0.430

0.609

1.039

 

3

Alex Rodriguez

NYY

124

130

0.321

0.421

0.610

1.031

 

4

Travis Hafner

CLE

94

108

0.305

0.408

0.595

1.003

 

5

David Ortiz

BOS

119

148

0.300

0.397

0.604

1.001

 

6

Manny Ramirez

BOS

112

144

0.292

0.388

0.594

0.982

 

7

Carlos Delgado

FLA

81

115

0.301

0.399

0.582

0.981

 

8

Todd Helton

COL

92

79

0.320

0.445

0.534

0.979

 

9

Jason Giambi

NYY

74

87

0.271

0.440

0.535

0.975

 

10

Jason Bay

PIT

110

101

0.306

0.402

0.559

0.961

 

2004 Season

 

Rank

PLAYER

TEAM

Runs

RBI

BA

OBP

SLG

OPS

 

1

Barry Bonds

SFO

129

101

0.362

0.609

0.812

1.422

 

2

Todd Helton

COL

115

96

0.347

0.469

0.620

1.088

 

3

Albert Pujols

STL

133

123

0.331

0.415

0.657

1.072

 

4

Jim Edmonds

STL

102

111

0.301

0.418

0.643

1.061

 

5

Adrian Beltre

LOS

104

121

0.334

0.388

0.629

1.017

 

6

Lance Berkman

HOU

104

106

0.316

0.450

0.566

1.016

 

7

Manny Ramirez

BOS

108

130

0.308

0.397

0.613

1.009

 

8

Scott Rolen

STL

109

124

0.314

0.409

0.598

1.007

 

9

J.D. Drew

ATL

118

93

0.305

0.436

0.569

1.006

 

10

Travis Hafner

CLE

96

109

0.311

0.410

0.583

0.993

 

2003 Season

 

Rank

PLAYER

TEAM

Runs

RBI

BA

OBP

SLG

OPS

 

1

Barry Bonds

SFO

111

90

0.341

0.529

0.749

1.278

 

2

Albert Pujols

STL

137

124

0.359

0.439

0.667

1.106

 

3

Todd Helton

COL

135

117

0.358

0.458

0.630

1.088

 

4

Gary Sheffield

ATL

126

132

0.330

0.419

0.604

1.023

 

5

Carlos Delgado

TOR

117

145

0.302

0.426

0.593

1.019

 

6

Manny Ramirez

BOS

117

104

0.325

0.427

0.587

1.014

 

7

Jim Edmonds

STL

89

89

0.275

0.385

0.617

1.002

 

8

Alex Rodriguez

TEX

124

118

0.298

0.396

0.600

0.995

 

9

Trot Nixon

BOS

81

87

0.306

0.396

0.578

0.975

 

10

David Ortiz

BOS

79

101

0.288

0.369

0.592

0.961

 

2002 Season

 

Rank

PLAYER

TEAM

Runs

RBI

BA

OBP

SLG

OPS

 

1

Barry Bonds

SFO

117

110

0.370

0.582

0.799

1.381

 

2

Jim Thome

CLE

101

118

0.304

0.445

0.677

1.122

 

3

Manny Ramirez

BOS

84

107

0.349

0.450

0.647

1.097

 

4

Brian Giles

PIT

95

103

0.298

0.450

0.622

1.072

 

5

Jason Giambi

NYY

120

122

0.314

0.435

0.598

1.034

 

6

Larry Walker

COL

95

104

0.338

0.421

0.602

1.023

 

7

Alex Rodriguez

TEX

125

142

0.300

0.392

0.623

1.015

 

8

Vladimir Guerrero

MON

106

111

0.336

0.417

0.593

1.010

 

9

Todd Helton

COL

107

109

0.329

0.429

0.577

1.006

 

10

Sammy Sosa

CHC

122

108

0.288

0.399

0.594

0.993

 

2001 Season

 

Rank

PLAYER

TEAM

Runs

RBI

BA

OBP

SLG

OPS

 

1

Barry Bonds

SFO

129

137

0.328

0.515

0.863

1.379

 

2

Sammy Sosa

CHC

146

160

0.328

0.437

0.737

1.174

 

3

Jason Giambi

OAK

109

120

0.342

0.477

0.660

1.137

 

4

Luis Gonzalez

ARI

128

142

0.325

0.429

0.688

1.117

 

5

Todd Helton

COL

132

146

0.336

0.432

0.685

1.116

 

6

Larry Walker

COL

107

123

0.350

0.449

0.662

1.111

 

7

Lance Berkman

HOU

110

126

0.331

0.430

0.620

1.051

 

8

Jim Thome

CLE

101

124

0.291

0.416

0.624

1.040

 

9

Chipper Jones

ATL

113

102

0.330

0.427

0.605

1.032

 

10

Alex Rodriguez

TEX

133

135

0.318

0.399

0.622

1.021

 

2000 Season

 

Rank

PLAYER

TEAM

Runs

RBI

BA

OBP

SLG

OPS

 

1

Todd Helton

COL

138

147

0.372

0.463

0.698

1.162

 

2

Manny Ramirez

CLE

92

122

0.351

0.457

0.697

1.154

 

3

Carlos Delgado

TOR

115

137

0.344

0.470

0.664

1.134

 

4

Barry Bonds

SFO

129

106

0.306

0.440

0.688

1.127

 

5

Jason Giambi

OAK

108

137

0.333

0.476

0.647

1.123

 

6

Gary Sheffield

LOS

105

109

0.325

0.438

0.643

1.081

 

7

Vladimir Guerrero

MON

101

123

0.345

0.410

0.664

1.074

 

8

Frank Thomas

CHW

115

143

0.328

0.436

0.625

1.061

 

9

Sammy Sosa

CHC

106

138

0.320

0.406

0.634

1.040

 

10

Jeff Bagwell

HOU

152

132

0.310

0.424

0.615

1.039

 

In 2006 only one player (Albert Pujols) ranked in the top ten in OPS, RBIs and Runs Scored.

In 2005 four hitters (Pujols, Alex Rodriguez, David Ortiz and Manny Ramirez) ranked in the top ten in all three categories.

In 2004 only Pujols again ranked in the top ten in all three categories.

In 2003 five hitters (Pujols, Rodriguez, Todd Helton, Gary Sheffield and Carlos Delgado) ranked in the top ten in all three categories.

In 2002 only Alex Rodriguez and Jason Giambi ranked in the top ten in all three categories.

In 2001 five hitters ranked in the top ten in all three categories.

In 2000 Todd Helton and Jeff Bagwell were the only hitters ranked in the top ten in all three categories.

What then do we make of the OPS statistic. Since 2000 in less than 30% of the time does a player ranked in the top ten in OPS also rank in the top ten in Runs scored and RBIs. OPS is therefore a poor measure of players’ performance when it comes to run contribution (whether scored or driven in). Given that runs is the true determination of wins and losses then shouldn’t we be utilizing a metric other than OPS that also considers the hitter’s ability to score runs and contribute via RBIs.

The second limitation of OPS is that it double-counts the number of hits that a player has. Since the total number of hits is already counted in both on-base average and slugging percentage then using OPS will naturally be biased towards players with a high batting average.

There is also a third limitation of the OPS measure. At its heart it aggregates On-Base Percentage (which divides Hits, Walks and Hit-by-Pitch by a measure resembling total Plate Appearances) and Slugging Percentage (which takes Total bases and divides by total At-Bats). This is like adding apples and oranges.

The denominator for On-Base Percentage is Plate Appearances, whereas it is At-Bats for Slugging Percentage. It is a basic premise of addition that one cannot add two fractions with different denominators unless certain adjustments are first made. Again, it is like adding apples and oranges. What does an OPS of 1.000 mean, for eg.

Intuitively we know that a batting average of 0.300 represents three hits in ten at-bats. An on-base average of 0.400 means getting on-base in 4 out of every ten plate appearances. And a slugging percentage of 0.600 (or 60%) means 6 total bases for every ten at-bats. However, an OPS of 1.000 means what exactly? Does it mean 1 hit for every at-bat. NO. Then does it mean 1 time on base for every plate appearance. Definitely Not. Well then it means absolutely nothing since its adding two very different numbers. The OPS adds two fractions with different denominators which renders it practically meaningless. Literally like adding apples and oranges. Hence the results cannot be properly interpreted. Therefore the statistic called OPS is not a true statistical measure. Just because it may produce plausible results from time to time does not mean that it is an accurate measure. Likewise, the OPS with all its flaws is also limited in its ability to indicate the top run contributors in the game.

2008 PER Sports, Inc.

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