There is a perception among baseball observers that there is empirical evidence that restricting pitcher workloads (through pitch counts, innings pitched caps, days between starts/reliever appearances, etc.) helps to lower injury rates and to increase pitcher effectiveness. The thing is, at least when it comes to injury prevention, the data simply doesn't exist.
BPro's Pitcher Abuse Points system has never been correlated with higher arm injury rates among the annual league leaders. The same thing goes for a simpler correlation between high average pitch counts and arm injuries. There has never also been a correlation shown between high pitch counts and an arm injury occuring one week, one month or even one year from the date of that start. There is no correlation shown between a young pitcher exceeding his innings pitched cap and increasing his liklihood of injury the subsequent season.
In short, there is no evidence suggesting that the modern attempts to restrict pitcher workloads is keeping them healthier. If such evidence does exist and you know of it, please leave a comment and point me in that direction.
Now, when it comes pitcher effectiveness, there is more evidence that restricting workloads can be beneficial. It's easy to look at how a starter performs on four, five or six days rest and see there is a general trend toward increased effectiveness with additional days off. Same goes for reliever use - they generally get less effective the longer they go without a game off in between. That said, there are some other questions to be asked:
* Has baseball created less durable pitchers by restricting their workloads throughout their professional career?
* Could today's starters be effective on three days' rest, if they were trained to do so?
* Could those same starters throw 120 or 130 pitches a game and see no ill effects (injury or ineffectiveness) if they were trained to do so?
* Could today's relievers pitch effectively in multi-inning appearances (even throwing as many as 40 or 50 pitches) if they were trained to do so?