Originally Posted by AtomicDumpling
Teams have been using innings limits in baseball for 30+ years, so this is nothing new. For a century it was standard practice for pitchers to throw 300 or even 400 innings per year. Here is a list of the league leaders in innings pitched
per season. Eventually teams realized that pitchers performed much, much better when they were not worked so hard. In baseball history there have been 826
times where a pitcher threw 300+ innings in a single season. Know when the last time a pitcher hurled 300+ innings was? Steve Carlton way back in 1980, 33 years ago. It has been 25 years since a pitcher threw even 275 innings. Even before sabermetrics, people began to realize that a pitcher was much less effective as his pitch counts rose during a game. They also saw that players tended to get injured or have their performance suffer after a long game with a lot of pitches thrown.
Not disagreeing with your premise at all but another important reason for the reduction of innings by starters is the demise of the 4 man rotation. Assuming an even number of starts among all the members of the staff, a 5 man rotation would average 32.4 starts per 162 games but a 4 man rotation would average 40.5 starts, a difference of 8.1 starts. Not way that starts can be manipulated an ace may get a couple more but most years the league leader in starts is at 35 games and none have reached 37 games since 1991. In the 1970's however the league leader was typically in the low 40's. (Historically it seems that this was a high period but 40 seemed typical in the 4 man era, remember shorter season pre-1961.) http://www.baseball-reference.com/le..._top_ten.shtml
Assuming 5-7 starts lost to the change in rotation size would reduce inning load from 30 to 50 innings per season without even getting into pitch counts.