The Kansas City Royals rotation isn’t going to be great this year. That’s pretty much a given. It’s not, however going to be as bad as some hyperbolic fans and media would lead you to believe. If someone suggests this rotation is going to be historically bad, then that’s a good sign you should look elsewhere for well thought out baseball discussion. However, there is plenty of merit to the idea that the Rotation isn’t going to be the backbone of this year’s team.
The Kansas City Royals bullpen however, is looking like it’s going to be very good. Having the best relief pitcher in baseball alone is enough to ensure it won’t be a terrible pen. Beyond Joakim Soria, the Royals have a nice group of players including Robinson Tejeda, Tim Collins, Jeremy Jeffress and Aaron Crow. It’s not a stretch to say that the Royals have one of the best bullpens in the American League.
This raises an interesting question. Can a team have a decent pitching staff with a lights out bullpen and a poor rotation?
In 2010 the average American League team ERA was 4.14 and the average team pitched about 1,444 innings of which about two thirds were thrown by the starting rotation. Using those numbers, I constructed the following table. The left column represents various ERA’s for the starting pitchers. The right column is the corresponding ERA that the relievers would have to put up in order for the team to have an ERA of 4.14. As a note of reference, the average AL starting rotation had a 4.26 ERA last year, while the average bullpen had a 3.89.
The bullpen has to be really, really good to make up for a poor starting rotation. It takes a historically good bullpen to make up for a pretty bad rotation. So, in order to be competitive with a poor rotation, a team would have to have not only a good bullpen, but shift more innings to the bullpen. They could also have an offense good enough to overcome a below-average pitching staff, or some combination of those.