It’s time to unveil one of my longer-running research projects. Offense has exploded over the past decade and a half in Major League Baseball, while at the same time the top pitchers of the age – Clemens, Maddux, Pedro, Randy Johnson – have stood further and further above the league. I’ve long suspected that these two phenomena were connected by a common fact: the percentage of each team’s innings thrown by its top pitchers has been in steep decline for years, and as a result each team – even if it has just as many or more quality arms as in years past – is delegating an ever-growing percentage of its innings to be thrown by second-line pitchers. I should note that this phenomenon is mostly independent of the dilution of pitching inherent in expansion.* In other words, the problem isn’t just that each team has fewer top pitchers because they are distributed more widely about the league – it’s that each team makes less use of the best pitchers it does have, and reaches deeper into its own staff, than in years past. Three trends have driven this revolution: the five-man rotation, which takes innings from the top four starters and gives it to #5; the decline in complete games and related decline in innings per start, which shifts innings from the rotation to the bullpen; and the increasing specialization of relievers, which takes innings away from the bullpen aces (now, just “closers”) and gives them to middle relievers.
We know all this, of course. But I wanted to quantify it, and if someone else has, I missed it.** So here’s what I did. I took one season every five years from 1920 – the dawn of the modern, lively-ball era – through 2004 (I would have used 2005 but I started the study last July). I went through each team in each league and identified their top six pitchers. For most of the study, that meant top 4 starters and top 2 relievers. For some of the 1920-35 period, I used the fifth starter in the bullpen column because teams generally had a swing man with irregular starting duties do most of the relief work.
Picking a top 6 is more art than science, though I mostly followed the listings in baseball-reference.com’s team pages. Wherever possible, I erred on the side of listing the better pitcher if there were two otherwise comparable workloads and usage patterns. I’ll discuss a few other specific methodological issues below the fold.*** In general, I sought to look at a team’s roster and figure out, from how it used its pitchers, who the team thought were its top 6. For example, I made sure to include Norm Charlton on the 1990 Reds even if it meant classifying him as the team’s fourth starter. While I used an every-five year interval, I was off a year in 1996 to avoid using a strike-shortened season, and in 1946 to avoid a year of war depletion. Without further ado, here are the results, with more notes to follow the charts.
By Rotation/Bullpen Slot
First, a breakdown of the average workload and ERA for each slot:
Year | SP1 | ERA | SP2 | ERA | SP3 | ERA | SP4 | ERA | RP1 | ERA | RP2 | ERA | Others | ERA | Lg ERA |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2004 | 207.8 | 3.83 | 193.1 | 4.19 | 160.9 | 4.56 | 139.7 | 4.62 | 66.4 | 3.10 | 78.5 | 3.33 | 600.0 | 4.99 | 4.46 |
2000 | 214.2 | 4.03 | 188.7 | 4.47 | 157.0 | 4.61 | 131.2 | 4.94 | 69.4 | 3.51 | 76.6 | 3.52 | 604.0 | 5.41 | 4.76 |
1996 | 222.1 | 3.83 | 198.5 | 4.43 | 173.8 | 4.47 | 132.9 | 4.82 | 68.3 | 3.31 | 79.8 | 3.38 | 573.0 | 5.30 | 4.61 |
1990 | 216.5 | 3.36 | 196.7 | 3.69 | 175.0 | 4.06 | 151.3 | 3.96 | 73.2 | 2.61 | 90.5 | 2.93 | 541.3 | 4.33 | 3.85 |
1985 | 237.2 | 3.18 | 220.1 | 3.79 | 180.2 | 3.81 | 147.0 | 4.06 | 91.1 | 2.93 | 91.1 | 3.27 | 481.6 | 4.57 | 3.89 |
1980 | 238.7 | 3.37 | 218.8 | 3.75 | 186.0 | 3.83 | 162.9 | 4.03 | 98.9 | 2.71 | 102.0 | 3.32 | 448.7 | 4.42 | 3.83 |
1975 | 260.9 | 3.05 | 229.7 | 3.69 | 193.5 | 3.74 | 154.8 | 3.92 | 91.2 | 3.11 | 95.2 | 3.29 | 421.4 | 4.23 | 3.70 |
1970 | 266.4 | 3.33 | 229.1 | 3.85 | 198.7 | 3.84 | 148.0 | 3.94 | 91.4 | 3.01 | 86.8 | 3.43 | 431.6 | 4.50 | 3.88 |
1965 | 258.6 | 3.04 | 227.1 | 3.24 | 190.7 | 3.56 | 161.2 | 3.63 | 103.5 | 2.67 | 86.6 | 2.97 | 431.2 | 4.13 | 3.50 |
1960 | 250.8 | 3.42 | 215.0 | 3.55 | 181.6 | 3.69 | 156.7 | 3.62 | 98.3 | 3.17 | 101.9 | 3.57 | 383.2 | 4.60 | 3.82 |
1955 | 230.8 | 3.36 | 206.7 | 3.70 | 175.0 | 4.00 | 148.1 | 3.75 | 97.3 | 3.20 | 104.4 | 3.73 | 413.3 | 4.84 | 4.00 |
1950 | 261.7 | 3.60 | 217.9 | 3.97 | 199.4 | 4.13 | 150.9 | 4.48 | 114.9 | 4.26 | 104.4 | 4.78 | 323.8 | 5.22 | 4.36 |
1946 | 244.5 | 2.78 | 209.1 | 2.94 | 178.3 | 3.46 | 140.5 | 3.34 | 90.9 | 3.27 | 121.2 | 3.14 | 399.5 | 4.35 | 3.46 |
1940 | 253.7 | 3.26 | 223.7 | 3.67 | 185.8 | 4.34 | 160.4 | 3.94 | 99.8 | 3.97 | 96.7 | 4.16 | 358.0 | 4.98 | 4.11 |
1935 | 261.5 | 3.52 | 220.5 | 3.76 | 187.5 | 3.95 | 163.7 | 4.33 | 141.6 | 4.11 | 111.6 | 4.33 | 280.7 | 5.44 | 4.24 |
1930 | 260.9 | 3.87 | 224.1 | 4.41 | 200.2 | 4.82 | 164.5 | 4.72 | 134.8 | 4.72 | 98.3 | 5.33 | 283.5 | 5.89 | 4.81 |
1925 | 252.3 | 3.70 | 232.1 | 3.88 | 205.2 | 4.08 | 176.5 | 4.40 | 139.6 | 4.69 | 109.5 | 4.66 | 248.9 | 5.20 | 4.33 |
1920 | 286.8 | 2.96 | 273.0 | 2.96 | 236.8 | 3.61 | 193.9 | 3.57 | 129.3 | 3.54 | 88.2 | 3.64 | 183.1 | 4.52 | 3.46 |
Innings are rounded to the nearest tenth. The every-five-years pattern does miss a few things; since 1970 was a hitters’ year we basically skip the whole 1966-74 period. And you can see that workloads were mostly off in 1946, as managers spread their work around with pitchers returning from the war; those numbers would be more dramatic except for Lou Boudreau’s decision to throw Bob Feller and his 2.18 ERA for 371.1 innings in pursuit of a sixth place finish. Also, bear in mind the switch to the 162-game schedule in 1961, which added 72 innings a year to each staff’s workload, as well as the (not counted here) dramatic expansions in the size of the postseason from 4-7 games through 1968, to 7-12 games in 1969, to 8-14 games in 1985, to 11-19 games in 1995. A World Championship team in 1955 could expect to throw 1449 innings if it extended the postseason to its logical limit; by 1996, that number was 1629.
For recent history, you can see vividly that front-line pitcher workloads have fallen off sharply in the past 20 years, much more sharply than in any prior period, and that it’s affected both starters and relievers. Without compelling evidence that this has reduced pitcher injuries, I can’t see how you justify this, although you could argue that the modern postseason makes it a necessity. Until about 1930, a team’s #1 starter would pitch more innings than the whole second-line staff; now, the second-line pitchers throw nearly three times as many innings as the ace.
One of the more dramatic changes comes when you trace the use of the bullpen before and after 1950. From 1955 on, you can see clearly defined #1 and 2 relievers on most teams; from 1940 to 1950, there are guys who have those jobs on most teams, but their ERAs are usually around the league ERA rather than far superior; prior to 1940, I was largely counting in those slots guys who were doing most of their work as spot starters.
Rotation/Bullpen Shares of the Workload
Next, the breakdown by starters, relievers, their performance and share of the workload. “Adv” is the ERA of the rest divided by the ERA of the top 6 (i.e., the percentage advantage of the top 6 in quality vs. the rest).
Year | SP% | ERA | RP% | ERA | S+R% | ERA | Rest% | ERA | Adv |
---|---|---|---|---|---|---|---|---|---|
2004 | 48.5 | 4.25 | 10.0 | 3.23 | 58.5 | 4.08 | 41.5 | 4.99 | 1.22 |
2000 | 48.0 | 4.46 | 10.1 | 3.52 | 58.1 | 4.29 | 41.9 | 5.41 | 1.26 |
1996 | 50.2 | 4.33 | 10.2 | 3.35 | 60.4 | 4.16 | 39.6 | 5.30 | 1.27 |
1990 | 51.2 | 3.74 | 11.3 | 2.79 | 62.5 | 3.56 | 37.5 | 4.33 | 1.22 |
1985 | 54.2 | 3.66 | 12.6 | 3.10 | 66.7 | 3.55 | 33.3 | 4.57 | 1.29 |
1980 | 55.4 | 3.71 | 13.8 | 3.02 | 69.2 | 3.57 | 30.8 | 4.42 | 1.24 |
1975 | 58.0 | 3.54 | 12.9 | 3.20 | 70.9 | 3.48 | 29.1 | 4.23 | 1.21 |
1970 | 58.0 | 3.70 | 12.3 | 3.21 | 70.3 | 3.62 | 29.7 | 4.50 | 1.25 |
1965 | 57.4 | 3.33 | 13.0 | 2.81 | 70.4 | 3.23 | 29.6 | 4.13 | 1.28 |
1960 | 57.9 | 3.55 | 14.4 | 3.37 | 72.4 | 3.52 | 27.6 | 4.60 | 1.31 |
1955 | 55.3 | 3.68 | 14.7 | 3.48 | 70.0 | 3.63 | 30.0 | 4.84 | 1.33 |
1950 | 60.4 | 3.99 | 16.0 | 4.51 | 76.4 | 4.10 | 23.6 | 5.22 | 1.27 |
1946 | 55.8 | 3.07 | 15.3 | 3.20 | 71.1 | 3.10 | 28.9 | 4.35 | 1.40 |
1940 | 59.8 | 3.75 | 14.3 | 4.07 | 74.0 | 3.81 | 26.0 | 4.98 | 1.31 |
1935 | 60.9 | 3.84 | 18.5 | 4.20 | 79.5 | 3.92 | 20.5 | 5.44 | 1.39 |
1930 | 62.2 | 4.40 | 17.1 | 4.98 | 79.2 | 4.52 | 20.8 | 5.89 | 1.30 |
1925 | 63.5 | 3.98 | 18.3 | 4.68 | 81.8 | 4.14 | 18.2 | 5.20 | 1.26 |
1920 | 71.2 | 3.23 | 15.6 | 3.58 | 86.8 | 3.30 | 13.2 | 4.52 | 1.37 |
There’s a lot of different competitive factors at work here over time – expansion, war, integration. But if diminishing the workloads of frontline pitchers was really worth it, you would expect the “Adv” column to flatten out sharply as the work gets spread around more. It has flattened, buit only slightly – there’s still no difference between 1925 and 2000.
The League Level
The third table looks at the league totals, and also at how the league ERA would change if you adjusted the best/rest mix to a steady 70% over time. Innings totals are rounded off to the nearest whole:
Year | Teams | Top 6 IP | Rest IP | LgERA | Adj70 |
---|---|---|---|---|---|
2004 | 30 | 25393 | 18001 | 4.46 | 4.35 |
2000 | 30 | 25115 | 18121 | 4.76 | 4.63 |
1996 | 28 | 24509 | 16045 | 4.61 | 4.50 |
1990 | 26 | 23484 | 14073 | 3.85 | 3.79 |
1985 | 26 | 25133 | 12521 | 3.89 | 3.86 |
1980 | 26 | 26187 | 11667 | 3.83 | 3.83 |
1975 | 24 | 24604 | 10113 | 3.70 | 3.71 |
1970 | 24 | 24489 | 10358 | 3.88 | 3.88 |
1965 | 20 | 20552 | 8623 | 3.50 | 3.50 |
1960 | 16 | 16068 | 6131 | 3.82 | 3.84 |
1955 | 16 | 15394 | 6612 | 4.00 | 4.00 |
1950 | 16 | 16785 | 5181 | 4.36 | 4.43 |
1946 | 16 | 15751 | 6392 | 3.46 | 3.47 |
1940 | 16 | 16320 | 5728 | 4.11 | 4.16 |
1935 | 16 | 17383 | 4492 | 4.24 | 4.38 |
1930 | 16 | 17321 | 4536 | 4.81 | 4.93 |
1925 | 16 | 17843 | 3982 | 4.33 | 4.46 |
1920 | 16 | 19327 | 2930 | 3.46 | 3.66 |
There is probably no more dramatic set of numbers on this chart than the column here showing the explosive growth in the raw number of innings thrown eah year by pitchers who do not qualify as one of their team’s top six pitchers. The total is up 50% just since 1985 (while the total thrown by front-line pitchers hasn’t changed much, give or take a year-to-year variation, since 1970). It’s up 80% since 1975, and has tripled since 1960, and the 1960 figure doubled the 1920 total. Yes, a lot of that is a function of the growth in the number of teams, and so spread out over more games. But there’s just no way around the fact that an awful lot of the time of paying customers is spent watching lesser pitchers ply their craft.