There are two trains of thought when it comes to starting vs relieving in terms of health.
Some think that putting a guy in the rotation will get a guy injured because he has a higher workdload
But there are others that also think that a guy in the bullpen will get injured due to the infrequency and unpredictability of when to pitch, as opposed to the strict schedule that starters have.
Either way, McGowan will get injured.