Always judging health
Health is a difficult thing to factor in when judging a roster decision. Some injuries are just bad luck. However, some players are injury prone. When injury prone players become free agents, the market takes that into account and those players end up signing smaller contracts.
This current injury to Butler might just be bad luck. However, Butler also suffered an injury on August 6th in the minors last season. That injury prevented him from pitching for the rest of the year. So only time will tell if injuries continue to be a reoccurring problem for Butler.
Butler’s ability to start is another advantage that he brings to the Cubs roster. Butler has made 39 career major league starts. This includes the 11 starts he made for the Cubs last season. With both Mike Montgomery and Butler in the bullpen, the Cubs have their sixth and seventh starters at the major league level. Very few major league teams have such options available to them.
However, when moving a pitcher from the bullpen to the rotation, allowing that person to get stretched out (getting used to pitching five innings or more at a time) needs to be taken into consideration. Montgomery has specifically talked about the toll that bouncing back and forth between the rotation and the bullpen took on him physically last season.