Bill Mack vs. Sean O'Sullivan — Career Comparison

Sean O'Sullivan built a career as a starting pitcher and Bill Mack as a reliever — different jobs with different demands — but on the metrics that apply to both, a comparison is still worth making. Bill Mack posted stronger surface numbers — ERA 3 and WHIP 1.000 compared to 6.01 and 1.616 for Sean O'Sullivan. By the career numbers, Bill Mack had the better of this cross-role comparison — though era context would sharpen the verdict.