The Normal Number of Injuries

May 13, 2014

                I got a couple of questions to the effect of "Doesn’t it seem like there are more pitcher injuries already this year than there have ever been?", to which I replied inside my own head "No, what it actually seems like to me is that every season since I was 13 years old, people talked about there being more injuries this year than there ever were before."    There have always been injuries, but for some reason people don’t learn to expect them. . .or so it seems to me; I don’t know.   When you get old you kind of lose your internal registry on certain things; you can’t tell whether other things are moving faster or you’re moving slower.

                Anyway, it occurred to me that we could track this in a simple way by tracking the number of starts during the season which aren’t by one of a team’s first five starters.  If pitchers get injured, they have to use "other" starters, other than their first five.

Starts by "S6" and greater aren’t exactly the same as "pitcher injuries", because sometimes pitchers are lifted from the rotation for ineffectiveness, rather than injury, and sometimes other things happen—scheduling quirks, trades, minor injuries that cause a rotation pitcher not to make his first start until May 15, etc.    In general, we can say that when injuries increase, games started by pitchers not in the starting rotation at the start of the season increase, and when starts by pitchers not originally in the starting rotation increase, injuries have increased.

                Let’s establish the base lines.    I studied all teams since 1970, except for the strike-shortened 1981, 1994 and 1995 seasons; I left 1972 in the study.  I identified each pitcher’s "Opening Season Starting Rotation" as their first five starting pitchers of the season, and anyone else who started for them during the season as a 6th starter.

                In the first ten games of the season, Sixth starters average .07 starts per team, or 1% of all starts.

                In the first twenty games of the season, Sixth starters average .67 starts per team, or 3% of all starts.

                By the end of the season, Sixth starters average 26% of all starts:

Mark

Group

Teams

S6 Tot

S6 Avg

Pct

1

10

1122

80

0.1

1%

2

20

1122

757

0.7

3%

3

30

1122

2005

1.8

6%

4

40

1122

3769

3.4

8%

5

50

1122

5995

5.3

11%

6

60

1122

8548

7.6

13%

7

70

1122

11397

10.2

15%

8

80

1122

14555

13.0

16%

9

90

1122

17735

15.8

18%

10

100

1122

21180

18.9

19%

11

110

1122

24933

22.2

20%

12

120

1122

28872

25.7

21%

13

130

1122

32871

29.3

23%

14

140

1122

37113

33.1

24%

15

150

1122

41515

37.0

25%

16

160

1082

44645

41.3

26%

 

                Redundancy for the sake of clarity, at the risk of speaking to you all as if you were a classroom full if idjits, we can use this data, during the season, to check whether injuries to starting pitchers are or are not running ahead of schedule.

                This season—to answer the essential question of the project—the number of 6th starter starts is in fact clearly running high.     I’m not sure my count is right, because it is difficult to chase down disorganized data, but I have 35 6th starter starts in the majors through 20 games, or 1.17 per team, which is close to twice the normal number.

                Are the numbers different now than they were in 1970?   Yeah, they are, but not all that much different.   From 1970 to 1979, 6th starters made 24% of all starts.   In the last ten years it’s 27%.

                This chart tracks how the percentage of games started by pitchers who weren’t in the starting rotation at the beginning of the season changes as the season goes on:

 

Games

Pct

Games 1 to 10

1%

Games 11 to 20

6%

Games 21 to 30

11%

Games 31 to 40

16%

Games 41 to 50

20%

Games 51 to 60

23%

Games 61 to 70

25%

Games 71 to 80

28%

Games 81 to 90

28%

Games 91 to 100

31%

Games 101 to 110

33%

Games 111 to 120

35%

Games 121 to 130

36%

Games 131 to 140

38%

Games 141 to 150

39%

Games 151 to 160

43%

Games 153 to 162

43%

 

                So at this part of the season, early May, normally 10 to 15% of the games are being started by 6th starters or lower.

                The year in which 6th starters made the most starts was 2009; 6th starters made 1,561 starts in 2009, or 52 per team.   This dropped to 39 per team in 2010, 38 per team in 2011.  

                The 1973 Texas Rangers and the 2006 Kansas City Royals got only 49 starts total out of their first five starting pitchers, leaving 113 games (for each team) to be started by 6th starters.   As you might guess, this is not a good sign; both teams lost 100 games.   These are the teams with the most starts from 6th starters, and their won-lost records:

Focus Team

Year

Won

Lost

S6

Rangers

1973

57

105

113

Royals

2006

62

100

113

Athletics

1977

63

98

110

Orioles

1988

54

107

105

Rockies

1993

67

95

105

Giants

1990

85

77

101

Blue Jays

2002

78

84

100

Giants

1982

87

75

99

Devil Rays

2000

69

92

97

Orioles

2009

64

98

96

Devil Rays

2003

63

99

95

 

                There was exactly one team in the data which only used five starters.  That was the 2003 Mariners, and they finished 93-69.  The 2012 Reds (97-65) only had one start from a sixth starter, and several teams only had two.

                The winning percentage of 6th starters is actually not all that bad.   In the data there were 46,939 games started by 6th starters, with a won-lost record (for their teams) of 22,263-24,676, a winning percentage of .474.   That’s not that bad, but the thing is, the more starts you have that are out the rotation, the further down you’re getting into the organizational depth.   You’re not really talking about 6th starters; you’re talking about 7th starters, 8th, 9th, 10th, and on down.    Those guys who started the season as the #3 guy in Double-A aren’t going to come up and pitch well all that often.    I would guess you’re talking about a .485 winning percentage from true 6th starters, but .350 from the back-end guys, the guys who are pushed into major league roles when they shouldn’t be there.   The true sixth starter is very often the pitcher who started the season as the organization’s #1 minor league pitching prospect.

 
 

COMMENTS (7 Comments, most recent shown first)

bjames
It is not even a general indication of A TEAM'S health; it is less exact than that. My observation is that when there are more pitcher injuries, there will be more starts by pitchers not in the rotation at the beginning of the season. This is a question about generalized effects; it is not a question about the Atlanta Braves. This is the normal way in which generalized effects are measured--by tracing outcomes, not by tracing outcomes related to specific causes. We measure air pollution by measuring how much dirt is in the air, not by measuring how much dirt is being PUT into the air by automobiles, by busses, by trains and by campfires. You can measure THOSE issues separately, but focusing on those as a beginning point, rather than focusing on the amount of dirt in the air, is a distraction. . .if you try to measure the amount of pollution coming from each source and then add it up to estimate the amount of pollution in the air, you WILL get the wrong answer. I used the term "sixth starters" to speak about a general class of pitchers, explaining carefully that this did not in all cases relate to what we would call sixth starters in other contexts. This is a semantic issue, and continuing to focus on it is a waste of time.
9:56 AM May 19th
 
hotstatrat
I don't think this was intended to be an exact measure of a team's rotation health, but a general indication.​
2:34 PM May 14th
 
shthar
I first heard this about football, but it really applies to all sports.

It doesn't matter who has the best team, what matters is who has the fewest injuries.
2:26 PM May 14th
 
StatsGuru
I agree with Edward. By Bill's reckoning, the Braves have had five starts by sixth starters, but in fact every time through the rotation they are using at least two sixth starters.
9:27 AM May 14th
 
abiggoof
I'm wondering, however, with Tommy John surgery causing so many pitchers to miss entire seasons, if that fifth starter in the rotation is often really a sixth starter. Obviously, that's not just something that happens these days, as guys have had to miss full seasons before, but I think that's the surgery more people are thinking of. And in cases like Pineda the last two years, a guy who had a good shot at being the fifth starter misses out on the whole season.
8:41 AM May 14th
 
78sman
This is interesting. I'm curious about whether there is a difference by league, and possibly between teams who play in hitters' parks and those who play in pitchers' parks. For potential league differences, does having a DH put more pressure on pitchers, resulting in potential injuries. For park differences, does pitching in a hitters' park put more pressure on pitchers.
11:34 AM May 13th
 
Edward
I wonder if there's a way to track what goes on in Spring Training within this system.

Two Braves, Two Athletics, and Patrick Corbin are where all this talk started, right?
7:28 AM May 13th
 
 
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