Built Different or Skill Issue? A BaseRuns Game Show: Defense Edition

Last week, I began a series of pieces about team win-loss totals as estimated by BaseRuns, first by taking a broad look at the methodology and its limitations, then by zooming in on the offenses that deviate most notably from their BaseRuns assessment in the run scoring department. Let’s wrap up with a look at the defenses that sit furthest from their runs allowed approximation.
In the offense edition, I used a game show format to evaluate whether the perspective offered by BaseRuns has a point, or if there’s something its methodology is overlooking. We’ll keep that framework going for the defenses as well. Here’s a reminder of how it works:
To determine whether or not BaseRuns knows what it’s talking about with respect to each team, imagine yourself sitting in the audience on a game show set. The person on your left is dressed as Little Bo Peep, while the person on your right has gone to great lengths to look like Beetlejuice. That or Michael Keaton is really hard up for money. On stage there are a series of doors, each labeled with a team name. Behind each door is a flashing neon sign that reads either “Skill Issue!” or “Built Different!” Both can be either complimentary or derogatory depending on whether BaseRuns is more or less optimistic about a team relative to its actual record. For teams that BaseRuns suggests are better than the numbers indicate, the skill issue identified is a good thing — a latent ability not yet apparent in the on-field results. But if BaseRuns thinks a team is worse than the numbers currently imply, then skill issue is used more colloquially to suggest a lack thereof. The teams that are built different buck the norms laid out by BaseRuns and find a way that BaseRuns doesn’t consider to either excel or struggle.