John Costello vs. J. A. Happ — Career Comparison

J. A. Happ built a career as a starting pitcher and John Costello as a reliever — different jobs with different demands — but on the metrics that apply to both, a comparison is still worth making. John Costello led in run prevention (ERA+ 135 vs 96), home run suppression (HR9+ 115 vs 80), and skill-based run prevention (DICE+ 99 vs 88). J. A. Happ held the edge in walk avoidance (BB%+ 95 vs 91). Role difference aside, John Costello holds a clear edge on every meaningful shared measure.