The case against six-man rotations
The Royals, Rays and White Sox have used a six-man rotation this year
Using six starting pitchers would dilute how often a team's best starter is used
Offense would be further harmed if six-man rotations become the norm
Back in 1883, the Providence Grays played 98 games as part of the eight-team National League. Their top starter, Charles (Old Hoss) Radbourn, started 68 of them, and two pitchers combined for the other 30. In fact, the three hurlers accounted for all 871 innings pitched by the Grays that season. Over time, as the pitcher's mound was moved back, as hurlers were allowed overhand deliveries, to break their wrist, to move from mere action initiators to a weapon for the team in the field, more and more was asked of them from a skill standpoint, and less and less from a workload standpoint. One of the most clear trends in MLB history is a diminished quantity of work put on starting pitchers, from one guy carrying most of the load to three men, to four, and in the modern era, to five.
That trend, let's hope, is reaching its nadir in 2011. Four teams, including the AL wild-card-leading Yankees, have used a six-man rotation on occasion. That's 24 percent of a roster dedicated to players whose sole job is to work once a week, more or less. The idea that working less often will be an aid to health and effectiveness has been the biggest driver of the expansion of starting rotations, but even five-man rotations, the norm for the last quarter-century, have seemed to be the point of diminishing returns, where the loss in quality -- fifth starters taking innings from their betters -- was not made up for by gains in the performance or availability of the other four.
A five-man rotation, pioneered by the Dodgers and Mets in the 1970s, was at least a proactive move, an attempt to manage the large quantity of pitching talent each of those teams had. There were concerns about pitcher durability as their efforts to get strikeouts, to avoid the bats of ever stronger hitters, wore them down.
The six-man rotations we've seen of late don't have that same reason for being. In almost all cases, teams get there when they replace an injured starter by necessity, and the replacement does well. When the healthy starter returns, there's no obvious candidate to be replaced, so the team punts the decision and goes to a six-man rotation in the hopes that time solves the problem for it. The White Sox with Philip Humber -- who took Jake Peavy's rotation spot and pitched well enough to keep his job upon Peavy's return -- is the classic case. The Royals took the practice to an extreme when they went to a six-man rotation to accommodate Kyle Davies when Davies came off the DL. The Yankees with Philip Hughes and the Rays with Jeff Niemann are other teams that have been reluctant to put starters back in the rotation at the expense of another pitcher.
The early days of the five-man rotation, which wasn't adopted universally for some time, featured the largest workloads for starting pitchers in modern history, as teams pushed their starters longer in games, sensing that they could get more from pitchers working less frequently. When Billy Martin squeezed 93 complete games from his five-man rotation -- for an A's team that led the league in ERA -- though, the camel's back broke. All five members of that rotation, the oldest of whom was Rick Langford at 28, would suffer from injury and ineffectiveness in the years that followed. It was then that MLB backed away from riding its starters in the five-man rotation, one of the many steps that led us to 12- and 13-man pitching staffs today.
It's a math problem, really. You have to get so many innings from your pitchers, and you're looking for the best combination of performance and health. The debate between the four-man and the five-man was never settled in any real way, but teams voted with their decisions, and now pining for a four-man rotation inspires queries about your disenchantment with the young people on your lawn. Stretching to a six-man puts further strain on rosters already lacking hitting talent; one small part of the higher strikeout rates and lower scoring in today's game is that teams eat all kinds of bad matchups on offense late in games for lack of better options. There are no pinch-hitters any longer; teams don't platoon because they don't have the roster space. They're reduced to a bench with a backup catcher, a backup infielder and a backup outfielder. Teams with 13 position players occasionally have a single platoon or utility guy. Those fantastic strikeout rates you see from late-inning relievers are part and parcel with the growth of those bullpens. You're not facing Terry Crowley or Benny Ayala any longer, you're getting to mow down Robert Andino.
A six-man rotation modeled along the lines of what they do in Japan might work. Starters in Japan work once a week, and when they pitch, they rack up some heavy pitch counts. This is an extension of what happened in the U.S. in the 1970s and would be one acceptable model for a six-man rotation, whereby a team would have a five-man bullpen less geared towards tactical options -- the innings pitched per relief appearance are also at an all-time low.
That's not what we'll see, though. Pitchers working in a six-man rotation aren't being asked to go deeper into games, so a team still needs the bloated bullpen every manager has come to rely upon. The combination may make defensive managing easier, but it's reduced the options on offense to nearly nil. The six-man rotation also means that a team gets less work from its best pitchers at the expense of the others. In a strict four-man rotation -- which was a rarity -- an ace can get 41 starts. In a strict five-man rotation -- often a five-day rotation -- pitchers topped out around 35 starts, with occasional exceptions. Go with a six-man, and your No. 6 starter gets 27 starts, same as your No. 1. This is a horrible way to run a business, taking opportunities from your best and giving them to your worst.
The six-man rotation is a bridge too far. The balance between defense and offense is out of whack, and a baseball roster with more pitchers than position players should be derided. Instead, it's being aped. The six-man rotation is a cop-out, and teams would be better off making their choice and buying back that extra roster spot for a hitter than by getting less work from their best starting pitchers.