Welch - you are right about the 10 man staff, 4 man rotation being predominant up to the 70s. By 1980, the Os, for example, were more of a 4.5 man rotation (Flanagan, Palmer, McGregor, and Stone) (a/k/a Cy Young, Cy Old, Cy Future, and Cy Present), but still got another 15 or so starts from Dennis Martinez, Sammy Stewart, and Mike Boddicker. Note again that the Os concentrated their innings in a shorter rotation filled by elite pitchers even though they had a couple of great future starters on that roster. By comparison, the NYY of 1980 had a sort of hybrid, where Tommy john went about every 4th day as an old timer (36 starts), but most of the time they used 5 starters (Guidry 29, tom underwood 27, Tiant 25, Rudy May 17, Figueroa 9, Mike Griffin 9, G. Perry .
By the mid 80s at the latest, 5 man rotations were common.
In 1980, as another Orioles pitcher, Steve Stone, was on his way to winning the Cy Young, Flanagan determined the different stages of Cy: He was the reigning Cy Young. "[Jim] Palmer is Cy Old," he said. "Stone is Cy Present and Storm [Davis] is Cy Future. When you get hurt, you become Cy-bex. When you're done, you become Cy-onara."http://espn.go.com/mlb/story/_/id/6894031/mlb-cy-young-winner-mike-flanagan-1951-2011