More musing/spitballing....a 6-man rotation makes sense (at least in theory) when you've got a bunch of good, but not great starters and want to get another one in. Like... 3 WAR Baker 3 WAR Liriano 3 WAR Pavano 2 WAR Slowey 2 WAR Blackburn 2 WAR Joe Schmoe Maybe something like this allows you to push each individual starter a little deeper into each start, shifting some of those bullpen innings from a lesser reliever to that decent 6th starter. I don't see something like this working all that well though. While the idea of "more rest between starts = allow more pitches thrown = deeper into game" sounds good, in practice it likely falls apart in a hurry. A (too) strict adherence to pitch counts and the specialization of bullpens all but guarantees they would still get pulled early, often before they ever get tired. I do think the 4-man would be a viable option for a team with a lousy rotation, maybe 4 + a spot starter to give the "ace" an extra day of rest occasionally. Say we've got.... 3 WAR "ace" 1 WAR Eh 0.5 WAR Ugh 0 WAR Blech -1 WAR *sigh* Dump that last starter entirely, make him a mop-up/spot-starter and give those innings to someone else. Most of those other guys likely aren't good enough to throw more than 80-90 pitches per start anyway, they should be able to start a little more often given their lighter workload. If your "ace" goes out and throws a 110 pitch, 8-inning gem, then give your spot starter a game if you need to provide for a little extra rest. Or just stick to the fixed 5-man rotation with no start skipping, we wouldn't want to create too much work for the manager.