Just for kicks, I went to retrosheet and pulled the 1965 Dodgers schedule and compiled data on their 4-man starters -- Drysdale, Koufax, Osteen, and Podres:
Code:
Drys Koufax Osteen Podres
Starts 41 40 38 23
Days Rest
3 1 2 5 0
4 29 29 19 7
5 10 9 10 6
6 0 0 2 1
7 0 0 0 3
8 0 0 1 2
9 0 0 1 0
10+ 0 0 0 4
You can see they were brought back on even 3-days rest on occasion--though many of those were after short-stints the start before. The schedule resulted in about 25-30% of their starts being on 5 days' rest. There is, of course, no record of the number of pitches these guys threw in any particular game, but it's probably fair to say they experienced more than 120 on more than afew occasions.
Note that Podres had several 10-day+ layoffs, which I assume are due to nagging injuries. I admit to being blissfully ignorant on that front right now, but his usage pattern suggests as much.
Osteen's pattern is interesting. His longer spans appear to generally be related to shuffling of rotation to take advantage of the schedule and get Drysdale or Koufax more starts...or maybe due to match-ups. It doesn't appear he was really replaced (as if he were injured, or just pushed back).
The point being that a 4-man rotation results in several 5-day stints.