Frank Keffer vs. Mariano Rivera — Career Comparison

Looking at the career totals, Frank Keffer and Mariano Rivera are fairly close on the surface numbers. Mariano Rivera posted stronger numbers in ERA (2.21 vs 5.63) and WHIP (1.032 vs 1.500). Frank Keffer had the advantage in home runs allowed (0 per nine innings vs 0.5). By the career numbers, Mariano Rivera 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.