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Injury-prone players (October 14, 2003)

Posted 12:00 p.m., October 14, 2003 (#1) - Steve Treder(e-mail)
  Happy to do it, Tom.

This whole thing started with a thread about Jeffrey Hammonds during the week of February 16th ... I've been unable to unearth it in the archives recently (maybe someone smarter than me can figure out how to do it). Anyway the discussion centered around the question of whether injuries to players are more or less random, unpredictable. I asserted that they aren't random at all, that some players are clearly more injury-prone than others.

Walt Davis weighed in, as usual, with fairness and wisdom. He said that simply pointing out injury-prone versus durable careers from the past proved nothing, that if I were to test my thesis, I should predict in advance which players would likely get hurt and which would remain healthy.

So, I consulted my 2003 Baseball Register, and just compiled two lists: the first a list of 50 players who appeared to have not gotten hurt much in their careers, and the second a list of 50 players who did get hurt a lot. I excluded both pitchers and catchers from the lists, since both of those positions are obviously prone to causing injuries. Here are the two lists:

Non-injury-prone players:

Bobby Abreu
Garret Anderson
Marlon Anderson
Jeff Bagwell
Pat Burrell
Mike Cameron
Johnny Damon
Ray Durham
David Eckstein
Brad Fullmer
Jason Giambi
Luis Gonzalez
Troy Glaus
Shawn Green
Ben Grieve
Marquis Grissom
Vladimir Guerrero
Todd Helton
Andruw Jones
Chipper Jones
Jacque Jones
Ryan Klesko
Paul Konerko
Mark Kotsay
Carlos Lee
Derrek Lee
Terrence Long
Tino Martinez
Fred McGriff
Doug Mientkiewicz
John Olerud
Magglio Ordonez
Rafael Palmeiro
Neifi Perez
Juan Pierre
Albert Pujols
Jimmy Rollins
Richie Sexson
Randall Simon
Chris Singleton
Sammy Sosa
Miguel Tejada
Jim Thome
Michael Tucker
Todd Walker
Daryle Ward
Craig Wilson
Jack Wilson
Randy Winn
Todd Zeile

Injury-prone players:

Edgardo Alfonzo
Moises Alou
Rich Aurilia
Adrian Beltre
Ellis Burks
Sean Casey
Roger Cedeno
Greg Colbrunn
Jose Cruz Jr.
David Dellucci
Erubiel Durazo
Jermaine Dye
Jim Edmonds
Carl Everett
Cliff Floyd
Nomar Garciaparra
Jeremy Giambi
Alex S. Gonzalez
Juan Gonzalez
Rusty Greer
Ken Griffey Jr.
Carlos Guillen
Ricky Gutierrez
Jeffrey Hammonds
Bobby Higginson
Todd Hollandsworth
Geoff Jenkins
Nick Johnson
Brian Jordan
Barry Larkin
Edgar Martinez
Bill Mueller
Phil Nevin
Jay Payton
Aramis Ramirez
Manny Ramirez
Pokey Reese
Tim Salmon
Reggie Sanders
David Segui
Gary Sheffield
Junior Spivey
Shannon Stewart
Fernando Tatis
Mo Vaughn
Fernando Vina
Larry Walker
Rondell White
Matt Williams
Dmitri Young

The first list of players is slightly younger than the second, with an average birth year of 1971.6, while the second list has an average birth year of 1969.7. I would consider this to be relevant, but not such a huge difference as to explain any differences in injury rates by itself.

I kept everyone updated throughout the season on the days spent on the DL for players from both lists; if anyone can access the archived thread, they can see the montly updates. The season-ending tally is as follows:

11 of the 50 players from the non-injury-prone list went on the DL during the 2003 regular season, spending 503 total days on the DL. 27 of the 50 players from the injury-prone list went on the DL during the 2003 regular season, spending 2,190 total days on the DL, or 81.3% of the grand total of DL days for the 100 players.

While I expected the injury-prone players to get hurt more often, this result was far more dramatic than I anticipated. In our discussions, I said that if the difference between the two lists was within 10% or so, it should be considered inconclusive; obviously the difference was vastly more than 10%.

While obviously not the most exhaustive study possible, I certainly consider this quick-and-dirty little exercise to be a strong indicator that injuries are not at all a purely random event, and that a player's injury history is a very good indicator of his future injury likelihood.

Walt also owes me a beer! :-)

Anyone who wants the full details of each player's stints on the DL is free to email me, and I'll send you my spreadsheet.

Injury-prone players (October 14, 2003)

Posted 12:47 p.m., October 14, 2003 (#4) - Steve Treder
  "However, were any of those players on the DL in the last week of 2002, the prior season?"

Not to my knowledge. I tried to only pick players who were actively playing during spring training while I picked them, around March 1st.

I'll email you the spreadsheet, Tom, and you can go to town on it. I agree that controlling for age would be an important step; I misspoke earlier: the average birth year for the non-injury-prone players is 1972.9, and for the injury-prone players is 1971.0.

Injury-prone players (October 14, 2003)

Posted 5:58 p.m., October 21, 2003 (#26) - Steve Treder
  "What we want is really for a guy to have been on the DL for one ailment, and then been prone to be on the DL for another ailment."

Good point, although from the point of view of teams, it doesn't really make much difference whether the guy keeps going on the DL for a recurrence of the same injury or a new unrelated injury -- he's still out of action either way. And I guess my intuition is that a player who is likely to have suffered the recurrent type of injury in the first place is likely to have a body type (and/or conditioning regimen) that makes him susceptible to other injuries too. But the distinction would be interesting to try and test.

I'm pleased (and a bit surprised, frankly) that my little internet-equivalent-of-a-bar-bet has stimulated so much interest. Will Carroll has contacted me, and says he is probably going to write it up in an article on Baseball Prospectus. Science marches on!