Fred Hayner vs. Mark Mercer — Career Comparison

On the career pitching numbers, Mark Mercer posted a stronger line than Fred Hayner. Mark Mercer posted stronger numbers in ERA (4.7 vs 13.5) and WHIP (1.826 vs 3.000). By the career numbers, Mark Mercer had the better of this comparison — though ERA and WHIP alone don't account for era, park factors, or the defenses each pitcher worked behind.