Okay, so with the recent (re-)signing of Curt Schilling by the Red Sox, the idea started to bounce around about the Sox using a six-man rotation. My initial reaction was that this is a horrendous idea. However, as I've thought about it, I can see some merit to the six-man rotation, especially with a rotation like the one the Sox will sport next year.
Though most teams have some type of mix between veteran starters and young pitchers breaking in, the Sox seem to be an extreme case. Two pitchers nearing Social Security in Wakefield and Schilling, two very young arms in Buchholz and Lester, a young Japanese import who appeared to tire down the stretch in Matsuzaka, and (of course) Josh Beckett. Here's how I envision a six-man rotation could work for the Sox:
The rotation would function just like a regular five-man rotation, and each week one pitcher (non-Beckett division) would be rotated out and replaced with the pitcher who was skipped the week prior. In this way, the Sox would gain additional rest for Schilling and Wakefield (which could help with the age concerns) and Matsuzaka (thus enabling him to remain fresh and strong deeper into the season), while also keeping the innings down on Lester and Buchholz, allowing them to break into the Bigs more gradually. It would also have the benefit of throwing Beckett out on regular rest all season, so you'd still get 30-35 starts from your ace.
Now this all comes with the caveat that no plan survives contact with the enemy, but if/when someone goes down with an injury, the rotation could then be converted to a simple five-man rotation.
Obviously, this would not be perfect for all teams. But with a team with such an extreme distribution of young pitchers and old pitchers, there seems to be a certain elegance, to my mind, in experimenting with this. And many teams could use a similar model to break in pitching prospects (as opposed to sending them to the bullpen when they first come up).
I guess I don't have too many questions about this idea (beyond am I a total bunny-boiler for thinking it up?), but I thought it was one of my more interesting concepts (however admittedly few they may be...).