Impact of Piazza, Griffey can’t be overstated
old). Trout’s career batting statistics include a .305 batting average with a .400 on-base percentage and a .560 slugging percentage. At the end of Griffey’s age 24 season (1994), he was hitting .306 but ranked behind Trout with a .379 on-base percentage and a .541 slugging percentage. Griffey’s .920 OPS was earned during baseball’s offensive explosion when the average hitter had a .732 OPS. Trout’s .960 OPS was earned during slightly more conservative times (league average of .711).
Like Griffey, Trout also grades well in baserunning and defense. Trout’s offensive advantage means at this point he’s ahead of Griffey’s production at a similar age: 43.6 WAR to 37.0 WAR. This doesn’t necessarily mean Trout will always rank ahead of Griffey. Griffey’s top two seasons would come at age 26 and 27, when he compiled single-season WAR marks of 9.7 and 9.1 (reminiscent of Harper’s 9.9 WAR in 2015).
It’s harder to find a player such as Piazza. Catchers generally don’t hit like Piazza did (and in the rare cases they do, certainly not for as long as he did). Piazza had a staggering 160 OPS+ through age 29, a full 21 points ahead of the next-best player. That player happens to be 29-year old Buster Posey.
Posey is a career .308 hitter while slugging .483. That’s certainly a far cry from Piazza’s .333 and .575 slugging percentage through age 29. Piazza has the WAR advantage (37.2 to 31.6), but not by as much as you’d think based on the offensive gap.
Baseball-Reference’s WAR sees Posey as a slightly above-average defender while Piazza rates as slightly below average. Once again, you might have thought the gap would be larger based on Piazza’s terrible defensive reputation and Posey’s relative prestige.
New research on catcher defense released by Baseball Prospectus this year shows that Baseball-Reference’s WAR could be underrating Posey’s defense. Rather than the 25 runs above average for which Baseball-Reference gives Posey, Baseball Prospectus (which combines throwing, blocking, and pitch framing) rates him as 115 runs above average (leading to a difference in about 9 WAR).
Does that mean Posey was more valuable than Piazza? No. Piazza’s defensive reputation was hurt by his poor throwing. Throwing just happened to be the only thing we really knew how to measure about catcher defense in the 1990s.
Baseball Prospectus’ Ben Lindbergh wrote about Piazza’s defense for FiveThirtyEight.com, a statistical analysis site, and noted that Piazza was in fact the worst thrower of all time. But his blocking and pitch framing skills were exceptional.
Combining all components, Baseball Prospectus sees Piazza as worth 63 runs above average rather than 63 runs below average, which is where BaseballReference grades him. That’s a swing of more than 12 wins. If you only include his numbers through age 29, it’s about a five-win swing, meaning Posey still trails Piazza through age 29.
And so, while players with the ability to produce similar value on the diamond will come along, none might ever replace the impact Piazza and Griffey had on the game at their positions.
High Heat Stats is an affiliate of USA TODAY Sports Digital Properties.