I like to compare pitching to distance running as I am very familiar with the stresses of the latter. It's not the same because throwing different kinds of pitches with maximun intensity strains your arm more than the repetive motion of running. However, I think of frequency and duration of running is analagous to the frequency and duration of pitching. I think that running 33 half marathons in six months versus running 70 5ks in six months would each put a different kind of stress on the joints. Starting pitching has the risk of cumulative long-term wear and tear whereas relief pitching has more risk of acute injury due to max intensity and shorter recovery. Both are big risks, but I think that the routine of being a starting pitcher is easier to manage than the erratic use of relievers. There are pros and cons of each, but I don't think using a young pitcher in short relief versus starting is keeping him safer.