Jerry Koosman vs. Jim Peterson — Career Comparison

Jerry Koosman built a career as a starting pitcher and Jim Peterson as a reliever — different jobs with different demands — but on the metrics that apply to both, a comparison is still worth making. Jerry Koosman posted stronger surface numbers — ERA 3.36 and WHIP 1.290 compared to 5.27 and 1.665 for Jim Peterson. By the career numbers, Jerry Koosman had the better of this cross-role comparison — though era context would sharpen the verdict.