Mark Mercer vs. Willis Roberts — Career Comparison

On the career pitching numbers, Willis Roberts posted a stronger line than Mark Mercer. Willis Roberts posted stronger numbers in WHIP (1.521 vs 1.826) and home runs allowed (0.94 per nine innings vs 1.17). By the career numbers, Willis Roberts 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.