In the old days, there were just pitchers: not starters, not relievers, not closers, and certainly not lefty specialists. And pitchers were expected to pitch a complete game (and pick up some innings on their off days if one of the other pitchers fell short). In the days of “Spahn and Sain and Pray for Rain,” there were no fixed rotations, as such. You might save your best pitcher for when you were facing the best team—after all, why waste Josh Beckett against the Royals? But in the 50s, teams began to realize that pitchers could be used in relief, as a regular feature. This new strategy allowed managers to put their starting pitchers on a regular schedule, which also allowed those pitchers to start more games and pitch more innings. In the 60s, the four-man rotation became de rigeur and by the early 70s some teams even started fooling around with three-man rotations. But in the mid-to-late 70s this trend reversed, and by the 1980s all teams were firmly entrenched in five-starter mode, with only occasional forays back into four-starter territory in situations of dire need.

Given this trend, it’s not surprising that we witnessed, in the 2007 season, even stricter limitations on pitchers, especially young pitchers. Case in point: the Joba Rules, which carefully proscribed Joe Torre’s use of hardthrowing prospect Joba Chamberlain as a reliever, dictating that the young fireballer, who is slated to be a starter in 2008, could not be used on consecutive days and could not come in to the middle of an inning. We saw something similar with the highly-touted Clay Buchholz in the Red Sox organization. Clay was subject to a strict pitch count in each game and a strict innings limit over the course of the season; in fact, Theo Epstein had given instructions that Buchholz was to be removed from his no-hitter against Baltimore if his pitch count reached 120 (thankfully, he retired the final batter on his 115th pitch, a beautiful curveball). Sox fans hoping to see Buchholz take the hill in the postseason were disappointed when management shut him down, citing a rigid 155 innings limit for a skinny kid who started the season in Double A. While pulling any pitcher out of a no-hitter in the 9th is inexcusable, an innings limit is hard to argue with—just think of Anibal Sanchez, another rookie who threw a no-no for the Marlins in 2006 but threw just 30 innings this year before having season-ending surgery for a torn labrum in June.

Given these two trends—mandating kid gloves for young hurlers and limiting pitchers of all ages to a certain number of pitches—it is only a matter of time before we see the advent of the six-man rotation. We probably would have seen it before now if not for the expansion era and the resultant shortage of quality pitching. But these days, with plenty of young talent in the pipeline and plenty of old talent hanging on by their surgically reconstructed fingernails, the era of the six-pitcher rotation may have finally arrived.

It’s been a subject of growing discussion in Boston this month, as the Sox have six starting pitchers slated to go in 2008: Josh Beckett, Daisuke Matsuzaka, Curt Schilling, Tim Wakefield, Buchholz, and Jon Lester. Among fans, the six-man rotation has been discussed mostly because the Fenway Faithful are loath to see any of these players go: Beckett is the staff ace; everyone expects Dice-K to break out next year; the city practically demanded Theo find a way to re-sign Schilling; Wakefield is a perennial fan favorite, still pitches extremely effectively, and costs practically nothing; Buchholz has the no-no under his belt and nasty stuff at his fingertips; and Lester, in addition to being the clinching pitcher of the 2007 World Series, has had the city’s heart in his hands ever since his diagnosis with cancer last year.

But sentiment is no reason to make poor baseball decisions, and Theo and Co. are about as unsentimental a management team as exists in baseball: if, say, the Marlins call them this afternoon and offer them, say, Miguel Cabrera for Jon Lester, that’s a deal they’d make. But this morning, on WEEI’s morning talk show, Schilling himself explained some practical reasons why you just might see the six-starter scenario play out in Fenway Park next year. “Simple math tells you if they start out with Lester and Buchholz in the rotation and they make every start of the year, don’t miss a turn, that they won’t be able to pitch in September and October,” Schilling said, referring to the front office’s innings limits on their two crown jewels. In addition to the younsters, there’s the oldsters—Schilling referenced himself and Tim Wakefield, tacitly admitting that neither of them is exactly the innings-eating horse they once were. Plus, as Schilling also noted, Daisuke Matsuzaka was accustomed to pitching on a six-man rotation in Japan. Given the other factors at play here, and given their huge investment in Matsuzaka, the six-man rotation is something the Red Sox have to be considering. Plus, if someone gets hurt, you could just go to a regular, five-man rotation without too much disruption. As Schilling concluded, “There’s a lot of things that lend itself to this being just about the perfect storm if it’s going to happen.”

Has the era of the six-man rotation finally dawned? And if it has, are we happy about it?

I expect the real reason baseball will eventually return to the four-man rotation will be the simplest of all: it helps win games. The five-man rotation is not on that evolutionary path; it is a digression, a dead-end alley.

- Craig Wright, The Diamond Appraised, 1989

Today Bronson Arroyo is starting on three days rest instead of the usual four. Why? Because he marched into manager Jerry Narron’s office demanded to start a day sooner.

Bronson was anxious to end his personal four-game losing streak, and also wanted to set up the rotation so he could face the division rival St. Louis Cardinals twice before the end of the season instead of just once.  You gotta love a guy who wants the ball in the biggest situation, and is willing to - nay, demands to - pitch on short rest to get those chances, so naturally, Narron and pitching coach Tom Hume were not about to stand in his way, especially since Arroyo has been the ace of the staff for the Reds this year.

But Bronson also had another reason for wanting to pitch on short rest: he felt he would actually pitch better.  Bronson has noticed over the years that the more days off he has between starts, the less sharp his command is, and he is convinced that three days of rest is the most optimal.

“It just seems like we’re sitting around so much waiting to start with so many off-days all the time,” Arroyo said. “I’ve been wanting to go to a four-man rotation all year.”

A four-man rotation in this day and age? Is Bronson Arroyo crazy?

Actually, probably not. As starting pitchers are increasingly held to 100 pitches or less, they are finding that they recover much more quickly from starts and are anxious to get back out there.  For example, both Brad Penny and Aaron Sele of the Dodgers this year have volunteered for bullpen duty in between starts when an off day would force them to pitch on five days rest.

Moreover, evidence is mounting that a four-man rotation is not as detrimental to pitchers arms as managers have assumed for the last 20 years or so.  This past off-season, Baseball Prospectus’s Keith Woolner did a study which found that even in the days before the 100-pitch limit, pitchers who pitched on three days rest statistically did no better or worse than pitchers pitching on four days rest, and that whereas pitching over 100 pitches in starts correlated strongly to arm injury, pitching on three days rest correlated little or not at all.  Furthermore, evidence seemed to indicate that pitchers who pitched on three days rest but were held to a reasonable pitch count actually pitched better than pitchers pitching on four days rest.

Which is all to say that Bronson Arroyo, in addition to being a badass, may actually know what he is talking about. It seems reasonable to assume that with pitchers throwing far fewer pitches per start than ever before, they should be able to start a little more often.  After all, going from a five-man rotation to a four-man rotation only adds about 5 or 6 more starts per starter over the whole season.

If teams returned to the four-man rotation with today’s 100-pitch count limit, we could easily see a return of the 40-start, 275 IP, 25-win season, without a significant increase in the risk of injury. Moreover, teams with the daring to implement the four-man rotation would gain significant advantages over their opponents, allowing many more of their innings to be pitched by their best pitchers (20-30 less starts by a fifth-starter type), and clearing a roster spot for an extra reliever or bench player.