Revisiting the Myth of the Five-Man Rotation
The other day, Eno wrote something up about the importance of team depth, and about the importance of being able to measure it. I think the thing I like most about the A’s roster right now is how it’s so deep in so many places. The Cardinals, too, have given themselves some flexibility. Depth is something you never think about at first — at first, you’re simply focused on the top bits of the depth chart — but for as much as the need for particular depth is unpredictable, odds are those extra players are going to matter. Players who aren’t on the opening-day roster, or who aren’t starters, are going to end up responsible for attempted runs scored and attempted runs prevented.
I think most people have a good understanding that it matters to have starting-pitcher depth beyond the front five. At least, most people who hang around at places like FanGraphs. We all get that pitchers are volatile, and we all get that pitchers get injured. Yet still there’s a focus on just the first five, because no pitcher is individually super likely to break down, and if the five are good enough you should never need a replacement, right? People talk about filling out five-man rotations, but really, a team would be fortunate to lean on a five-man rotation, and I thought it could be useful to provide some updated numbers from the season most recently finished. Those sixth and seventh starters in a system — they’re going to get innings. Sometimes a lot of them.
