Disability Days in Major League Baseball – Statistical Data Included
Although some people may argue that from a spectator standpoint that baseball is no longer the “national pastime,” there are no team sports with more participants nor are there any activities more popular among the youth of the United States than baseball. Beyond the 750 major league players, there are approximately 2100 minor leaguers, 45,000 intercollegiate players, 433,684 high school participants, and nearly 2 million players in youth leagues.
Even using the most conservative estimates, baseball accounts for more than 50,000 injuries per year, with rates per 100 participants ranging from 2 in Little League to 58 in Major League Baseball. As is true in most sports, epidemiologic studies of baseball injuries are short in duration and give but a snapshot view of the injury problem. Save for the ongoing investigations performed by the National Collegiate Athletic Association, there are virtually no published, long-term surveillance efforts being undertaken in the sport.
In theory, the best epidemiologic studies should come from levels of play offering the most sophisticated levels of medical care. Certified athletic trainers, team physicians, comprehensive exposure data, and professionally maintained medical records are all necessary for the scientific study of sports injuries. If this is true then Major League Baseball should be the mother lode of data. In baseball, statistics are as much a part of the sport as bats and gloves, and medical statistics reside in this wealth of information.
The “disabled list” is a mandated part of Major League Baseball. It defines injuries in terms of time lost from participation, is employed by every major league team, has been used for decades, and resides in a single database. It has the potential for providing information concerning injuries sustained by participants at the highest level of play, who are provided sophisticated medical care, with the use of consistent definitions of injuries over long periods of time. This is the first attempt to examine these data from a medical perspective.
METHODS AND DEFINITIONS
We examined the most comprehensive summary of disabled list data from Major League Baseball as compiled by American Specialty Companies in their publications on Major League Baseball player disability analysis.[1-3] American Specialty is a large private company devoted exclusively to providing risk management products and services for the sports and entertainment industry worldwide. They have published four editions of the baseball analysis report. These volumes are based on reports sent by each team to the Office of the Commissioner of Major League Baseball. We used the second edition, consisting of data from 1989 through 1992, and the third and fourth editions, covering 1993 through 1999.[1,3] Thus, data from 1989 to 1999 are included in this report.
During most of the season, a major league team is allowed but 25 players on its team roster. Major League Baseball rules allow injured players to be placed on a disabled list, permitting replacement of the injured player while maintaining the 25-player maximum team roster. Unlike the team roster maximum of 25 players, the disabled list can contain any number of players.
To be placed on the disabled list, the player must be certified as unable to play, with a specific diagnosis made by the team physician. A signed form is then sent to the Office of the Commissioner. Once on the disabled list, the player cannot return to the active roster for a minimum of 15 days. The player can remain on the disabled list for as many days as necessary for him to be ready to return to play. The same player may appear on the disabled list more than once in a season.
Major League Baseball also has a 60-day disabled list, whereby the player placed on this list cannot return to the active roster for 60 days. Players with long-term injuries, such as those requiring surgery, are placed on this list. Players on this list are not counted against the maximum 25-man active team roster and are also not counted against the 40-man team roster. The 40-man team roster is a protected list that includes the 25-man active roster and 15 other players in the minor league organization who are exempt from certain draft rules of the league. Any player who is promoted from the minor league to the major league must be on the 40-man roster.
Injured Player. Any player who is placed on the disabled list by his individual team. The injury must be certified by the team physician.
Disabled List Days. This represents the number of days a player spent on the disabled list. One player on the list for 1 day equals 1 disabled list day. Two players on the list for 1 day each equals 2 disabled list days.
Major League Teams. From 1989 to 1992 there were 26 teams in the league, from 1993 to 1997 there were 28 teams, and from 1998 to 1999 there were 30 teams in the league. Averages are corrected for the number of teams playing in any given year. A player strike in 1994 and 1995 reduced the number of games played by an average of about 48 (30%) and 18 (11%) per team, respectively.
From the 1989 season through the 1999 season, 3282 players were on the disabled list for a total of 195,671 disabled list days. The average number of disabled list days per team was 640.6 per season. Table 1 contains the disabled list statistics for the 11 years of study.
Disabled List Days per Team and per Player by Season
Year Disabled list Average Disabled Average
reports disabled list list disabled list
reports/team days days/team
1989 266 10.2 14869 571.9
1990 231 8.9 12603 484.7
1991 260 10.0 15830 608.8
1992 283 10.9 17656 679.1
1993 300 10.7 17810 636.1
1994(a) 259 9.2 15724 561.6
1995(a) 295 10.5 15552 555.4
1996 321 11.5 19432 694.0
1997 351 12.5 20454 730.5
1998 349 11.6 22127 737.6
1999 367 12.2 23614 787.1
(a) Strike years.
Over the 11 years there appeared to be an increase in the number of players on the disabled list as well as of the total disabled list days. The number of players on the disabled list each year increased over the period of study (Fig. 1), as did the total disabled list days (Fig. 2). The increase was still present when the total days were adjusted for the increasing number of players by examining the average disabled list days per team per year (Fig. 3). The increase means a positive slope for the regression line. If the lower 95% confidence interval for the slope (the dashed line with the smallest slope shown on the figures) has a positive slope, the slope of the regression line is statistically significantly positive (P [is less than] 0.05), since the lower confidence interval value for the slope is greater than zero.
The average number of days on the disabled list per disabled player varied over the period studied, revealing a slight but nonsignificant upward trend (Fig. 4). The regression line for average days per disabled list report per year had a low correlation coefficient ([r.sup.2] = 0.24), and the slope is only a 0.5-day increase per year and not significantly different from zero. After 1990, the slope of the regression line is essentially flat excepting 1995.
Table 2 shows the positions played by players on the disabled list. Over the 11 years, pitchers constituted an average of 48.4% of the disabled list reports (40.6% to 51.2%), representing 56.9% (46.8% to 62.5%) of the total disabled list days. Both the number of pitchers and the number of disabled list days lost by pitchers increased over the 11 years (Table 3). This pattern was seen among both starting and relief pitchers. However, neither the percentage of pitchers as disabled list reports nor the percentage of disabled list days lost for pitchers appeared to increase over the same period of time (Table 3).
Disabled List Reports by Player Position
No. of disabled Percentage of total
Position list reports disabled list players
Pitcher 1590 48.4
Catcher 251 7.6
First base 176 5.4
Second base 202 6.1
Third base 166 5.1
Shortstop 249 7.6
Outfielder 648 19.7
Disabled List Reports and Days for Pitchers by Season
Year disabled Percentage of disabled Percentage of
list disabled list list disabled
reports reports days list days
1989 118 44.4% 8319 55.9
1990 114 49.4% 7440 59.0
1991 133 51.2% 9356 59.1
1992 115 40.6% 8255 46.8
1993 152 50.7% 10123 56.8
1994(a) 126 48.6% 9013 57.3
1995(a) 147 49.8% 9719 62.5
1996 153 47.7% 10770 55.4
1997 178 50.7% 11860 58.0
1998 172 49.3% 13274 60.0
1999 182 49.6% 13129 55.6
(a) Strike years.
The number of disabled list reports from other positions was appreciably smaller than the number for pitchers (average, 5.1 for third basemen to 19.7 for outfielders); thus, identifying meaningful and significant increases (or decreases) over the 11-year period is difficult. However, only second basemen failed to show an increase proportional to the increasing number of players on the disabled list. Increases that were statistically significant were few; only pitchers and third basemen had statistically significant increases over the period of observation.
Over the final 5 years of reporting, the Major League Baseball disability analysis identified the five most frequently injured anatomic regions (Table 4) and the total disabled list days for each.[1,3] Ignoring the strikingly higher numbers in 1999 for elbow and back injuries, only the elbow disabled list days exhibited what appeared to be a consistent increase over the 5-year period, similar to that seen for the total disabled list days during the same period of time. It is important to note, however, that the increase in disabled list days for elbow injuries represents only 26% of the total increase in total disabled list days, but slightly more than the 22% one would have expected from this anatomic region.
Disabled List Days by Injury Location
Year Shoulder Elbow Knee Wrist/hand Back
1995 4912 3484 1019 910 797
1996 5121 3692 1700 1389 918
1997 5256 4808 1167 981 942
1998 6884 4697 1799 1544 931
1999 5922 5582 1742 1348 1490
% DL days(a) 27.8 22.0 7.3 6.1 5.0
(a) Total disabled list (DL) days per anatomic region for the 5 years
as a percentage of total disabled list days during the same 5 years.
Examination of individual team statistics failed to reveal a single team with a disabled list profile similar to that seen when one examines the disabled list data over the 11 years of study. However, with only an average of about 10 disabled list players per team per year, the appearance or disappearance of only 2 or 3 players from the disabled list has an impressive impact.
Although the major league baseball player disability analysis is a compilation of the official reports submitted by each team to the league office, it is not a medical database. The medical data contained in it are primarily the anatomic regions involved in the injury. Although injury “types” are sometimes noted, the categories are not mutually exclusive and are often vague (for example, strain, surgery, “tear,” or weakness), making meaningful analysis impossible.
The data exclude information on both ends of the injury severity spectrum. “Minor” injuries are excluded because their period of projected disability would not exceed 15 days. “Major” injuries resulting in elective surgical management are also excluded if the operative procedure was performed after the season ended.
The strength of the data lies in two general areas, magnitude and consistency. The database includes all Major League Baseball teams over an 11-year period, consisting of 3282 injured players. The data are consistent because the rules governing the disabled list have remained constant over the 11-year period. There is no doubt, however, that in some instances factors other than medical information are used in making disabled list decisions. For example, a relatively trivial injury might prompt a disabled list designation if there is a “better” minor league player available to come in as a substitute. On the other hand, a “star” with a more severe injury might be kept off the disabled list if there is an outside chance he can return in fewer than 15 days. There is, however, no reason to think that such subjective, nonmedical decisions changed in some systematic manner over the years under examination.
These data allow epidemiologic examination of a very popular sport previously ignored at the professional level. The only other published report concerning the injury data on adult baseball at any level of expertise examined collegiate players from a single institution over a 3-year period.
Our data showed a gradual and significant increase in injuries over the past 11 years. If one compares the average annual number of disabled list reports from the first 3 years of the study to that from the last 3 years (252 and 355, respectively) the increase is greater than 40%. This finding cannot be explained by examining injury data from any single team. Indeed, only with the inclusion of all 30 teams was this increase evident.
Such an increase seems antithetical given that conventional wisdom holds that improvements in training and conditioning, better diagnostic methods, and more appropriate surgical intervention should have reduced injuries and resulted in fewer people on the disabled list, or, at the very least, shorter periods of disability. We have examined the data with the intent of looking for a factor (or factors) that might account for the increase. Is the increase a reflection of injury severity? Is it a result of changing roles of players in certain positions (namely pitchers)? Is it the result of more sophisticated diagnostic tests identifying more problems?
Effect of More Teams. Most of the data from this source are presented as numbers rather than rates. Thus, the increases seen here could in part be a function of the fact that there are more teams and more players than there were 11 years ago. From 1989 to 1992 there were 26 teams in the league, from 1993 to 1997 there were 28, and from 1998 to 1999 there were 30 teams in the league. This represents a 15.4% increase in the numbers of teams and players, substantially less than the 40% increase in numbers of disabled list reports over the same period of time. However, examination of the figures in Table 1 fails to reveal an abrupt increase in either disabled list reports or days for the years the new teams were added. These data suggest that the addition of the additional teams accounts for only part of the increase in disabled list reports and days.
Increase in Disabled List Days. The average number of disabled list days per season has increased more substantially than the number of players on the disabled list. Comparing averages from the first and last 3 years of study, the number of disabled list days increased 53%, compared with a 41% increase in numbers of disabled list players. The discrepancy between the increase in disabled list days and disabled list players is almost entirely due to the fact that pitchers spend more time on the disabled list than do players at other positions. However, the average number of days on the disabled list per disabled player has remained unchanged. These findings suggest that the increase in disabled list days is not the result of more sensitive diagnostic tests allowing the diagnoses of heretofore unrecognized injuries. These new injuries are significant ones resulting in an average of more than 55 days lost per injury–injuries unlikely to have been ignored regardless of the precision of diagnostic capabilities.
Position Played by Disabled List Players. Although the total time at risk (number of games) and number of players allowed per team have remained unchanged throughout the study, recent changes in pitcher use may have resulted in larger numbers of players (pitchers) being exposed to potential injury. Examination of the data reveals that pitchers’ injuries play a major role in the overall number of injuries. From 1995 through 1999, 47.0% of the players in Major League Baseball were pitchers, who made up 48.4% of players on the disabled list. Pitchers’ injuries appeared more severe because their injuries accounted for 56.9% of the disabled list days. Clearly the number of pitchers on the disabled list is increasing. Because the number of pitchers is so high, and they have a higher likelihood of staying on the disabled list longer than players at other positions, the pitchers’ experience dominates the disabled list compared with other positions. Although the relief and starting pitchers on the disabled list appear to reflect the increase in a similar fashion, the patterns are not completely clear for other positions; most positions experienced a gradual increase in disability days, but only pitchers and third basemen had increases that were statistically significant.
It is possible that only certain specific injuries have been increasing, driving the overall upward trend observed but concealed in the vague language of the disabled list. It is also possible that players who in earlier years would be out of organized baseball may now still be playing and getting on the disabled list more commonly than other players. If certain specific injuries are responsible for the increase, or if some combination of prevention, modern surgery, and sophisticated rehabilitation is keeping players playing longer, it cannot be determined from the Major League Baseball disability analysis reports.[1-3]
The value of global, long-term surveillance systems is in their potential for identifying injury trends not apparent from examining data of individual teams or for relatively short periods of time. Once documented, such trends require more focused, detailed analysis. Examples of the application of these principles include the problems of catastrophic cervical spine injuries in American football, eye injuries in ice hockey, and the higher incidence of ACL injuries in women’s soccer and basketball.
Many people believe that the improvements in training and conditioning, diagnostic methods, and surgical treatment over the last 11 years have reduced injuries and resulted in fewer people on the disabled list in Major League Baseball. Yet, such does not appear to be the case. There can be little doubt that the rates of injury in Major League Baseball, judging by those players entered on the disabled list, have not declined over the last decade. On the contrary, it appears that the numbers of players and player days on the disabled list have both increased. The addition of players from teams added to the league accounts for only part of the increase.
Examining individual team data and injury location did not reveal the source of the increase. Furthermore, although the number of pitchers on the disabled list is increasing, it is doing so at a rate similar to the total number of players on the disabled list, so the increase is not disproportionate for that one position. Nor does it appear that the increase in injuries is a result of more sensitive diagnostic tests allowing the diagnoses of previously unrecognized injuries. We do not see any obvious reason for this increase.
On the one hand we might conclude that because of the increase in disability days, sports medicine as an applied medical specialty has not performed as well as might be expected. On the other, it may be that certain injuries have in fact been reduced, while others have increased. Players who in previous times would be out of organized baseball may now be still playing, and perhaps are placed on the disability list more frequently than other players. Players with more medically severe injuries may be returning to play quicker. Unfortunately, shortcomings in the disabled list as a medical database do not allow the more detailed analysis of the specific diagnoses required to test these hypotheses. More accurate and complete diagnoses for the players on the disabled list would greatly increase its usefulness as a medical database for examining the changes over the years. Whatever the reason, it is significant that publicly available surveillance data, when viewed over an 11-year period, have identified a potential problem that deserves further attention.
The authors express their sincere thanks to the San Francisco Giants organization, and especially to Dave Groeschner and Barney Nugent, assistant trainers, and to Brian Sabean, general manager, for their continuing support of this project. We also thank American Specialty Companies, Inc., for sharing with us their disability analyses.
[1.] American Specialty Companies, Inc: REDBOOK: Major League Baseball Player Disability Analysis, 2000 Edition. Roanoke, IN, 2000
[2.] American Specialty Insurance Group: Major League Baseball Player Disability Analysis. Roanoke, IN, 1992
[3.] American Specialty Insurance Services: Major League Baseball Player Disability Analysis. Roanoke, IN, 1997
[4.] Garfinkel D, Talbot AA, Clarizio M, et al: Medical problems on a professional baseball team. Physician Sportsmed 9(7): 85-93, 1981
[5.] Griffin LY, Agel J, Albohm MJ, et al: Noncontact anterior cruciate ligament injuries: Risk factors and prevention strategies. J Am Acad Orthop Surg 8: 141-150, 2000
[6.] Hale CJ: Injuries among 771,810 little league baseball players. J Sports Med Phys Fit 1(2): 80-83, 1960
[7.] McFarland EG, Wasik M: Epidemiology of collegiate baseball injuries. Clin J Sport Med 8:10-13, 1998
[8.] National Collegiate Athletic Association: Injury Surveillance System–Baseball. Overlook Park, KS, National Collegiate Athletic Association, 2000
[9.] Pashby TJ: Eye injuries in Canadian amateur hockey. Am J Sports Med 7: 254-257, 1979
[10.] Seefledt V, Ewing M, Walk S. An Overview of Youth Sports Programs in the United States: Report to the Carnegie Council on Adolescent Development. East Lansing, MI, Institute for the Study of Youth Sports, 1992
[11.] Torg JS, Quedenfeld TC, Moyer RA, et al: Severe and catastrophic neck injuries resulting from tackle football. Del Med J 49: 267-275, 1977
Stan Conte(*)PT, ATC, Ralph K. Requa,[dagger] MSPH, and James G Garrick,[double dagger] MD
[double dagger]Address correspondence and reprint requests to James G. Garrick, MD, Centers for Sports Medicine, Saint Francis Memorial Hospital, 900 Hyde Street, San Francisco, CA 94109.
No author or related institution has received any financial benefit from research in this study.
COPYRIGHT 2001 American Orthopaedic Society for Sports Medicine
COPYRIGHT 2001 Gale Group