How bad can a player’s season be without spoiling shot at HOF?

Through Sunday, Jason Heyward was hitting just .149/.286/.298, whiffing on more than half of his swings at breaking balls.

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In November at Baseball Prospectus, we introduced the 50 percent probability test for future Hall of Fame induction.

For example: In major-league history, 20 of 40 position players with at least 2.1 wins above replacement (WAR) through age 20 made the Hall of Fame. The other 20 didn’t. Using history as our guide, we can conclude that a hitter who has produced 2.1 or more wins by age 20 is about as likely to make the Hall of Fame as not. Between Bryce Harper and Manny Machado — each of whom clears the threshold — we are likely watching one Hall of Famer. It’s certainly not rigorous statistical analysis, but it provides a quick statistical shorthand to describe a future Hall of Famer.

Overall, we found 28 position players who are half-likely to make it into Cooperstown. It’s mostly the names you’re thinking of (Pujols, McCutchen, Trout), minus a few names you’re thinking of (Posey and Puig are just short, for now), and plus a few names you aren’t thinking of. Among the probable plusses: Jason Heyward, a player in his fifth season who has never led the league in any offensive category, who has made only one All-Star team, and who has received less MVP support during his career than Carlos Ruiz has.

Heyward’s value has come mainly from excellent defense, which has helped cover for his just-above-average hitting. But this year that offense has dropped to something much worse: Through Sunday, he was hitting just .149/.286/.298, whiffing on more than half of his swings at breaking balls. It’s very early, and the odds (and projection systems) favor his chances of fixing his stats as the year progresses. But what if he doesn’t? Using Baseball Prospectus’ WARP, we put his play this year at a tick below replacement level, which leads to a different kind of Hall of Fame threshold question: How bad can a player’s season be without permanently disrupting his shot at immortality?

The answer: Pretty, pretty, pretty bad. We went looking for the worst seasons by Hall of Fame hitters since 1950. We excluded Veterans Committee inductees, who generally weren’t as good as the Hall of Famers elected by writers. We ignored seasons in which the player didn’t reach 100 plate appearances, because we’re not looking for seasons entirely disrupted by injury. We measured the players by WARP, our total-value metric at Baseball Prospectus. And we did this for each age. Here we go:

AROUND THE HORN

We generally have an idea of what a Hall of Famer looks like. He has bold numbers all over the back of his baseball card, he wins hardware, he puts up a long run of four, five, six, seven-win seasons. He’s a shortstop who hits 500 home runs, like Banks. He sets all-time records, like Ripken and Brock. He wins batting titles, like Gwynn, or MVP awards, as more than half of these guys did.

But tucked into even the best careers are all sorts of fluctuations, extended passages where Hall of Famers looked like nothing of the sort. The reasons are varied; in some cases, the reasons might well be nothing more than bad luck or random fluctuation:  

When McCovey was 26, his dad died. He developed a painful foot injury. His manager questioned whether the injury was real, according to Mark Armour, writing for the SABR baseball biography project. An MVP candidate at age 25, and an MVP candidate at age 27, McCovey hit just .220 with 18 home runs at age 26. His defense cratered. His WARP dropped from 6.3 to 0.7. The Giants lost the National League pennant by just three games, easily accounted for by McCovey’s lost season.

Ripken had the best WARP at age 30 of any of our Hall of Famers, with 10.7. A year later, he had the lowest age-31 WARP in the group. His defense got more than 30 runs worse, according to Baseball Prospectus’ defensive metric, FRAA. His batting average on balls in play dropped by more than 50 points — whether a result of luck or bad contact — and he managed barely half of the 85 extra-base hits he had the previous season. In Harvey Rosenfield’s biography of Ripken, he notes that the shortstop’s contract negotiations with his team had dragged far into the season. Ripken wanted $39 million in guaranteed money; the Orioles were offering only a quarter of that. “Cal later admitted that the negotiations were a big distraction and may have affected his play,” Rosenfield writes in “Iron Man.”  

Dawson received MVP votes each year from age 24 to 28, and in four of five years from 32 to 36. But from 29 to 31, years that should have been part of his physical prime, he fell below average. As Jonah Keri recounts in "Up, Up & Away," Dawson was always “playing through loads of pain, his knees getting worse with every passing season on the Big O’s unyielding cement turf. He’d have his knee drained three times a year, since it would build up 10 times as much fluid as the average player’s; each procedure would get chased with a cortisone shot, which hurt like hell. His knees still throbbed every day.”

In their worst moments, these legends looked no better than the last man on the bench. Do you remember Lenny Harris? The career pinch-hitter who retired with 37 home runs in 18 seasons split between eight cities? He’s got one of the lowest career WARPs in Baseball Prospectus’ database. Here’s the imagined career of our Hall of Fame misfit, pieced together only from the worst parts of each Hall of Famer’s career, and charted against Lenny Harris’ career:

It’s hard to imagine that Jason Heyward, in his age-24 season this year, will challenge Tony Perez’s -0.6 HOF floor.  If he does, it will put him in unprecedentedly ignominious territory, to be sure. But if he — or any of your other favorite Hall of Fame candidates — has a truly lousy season this year, remember that, in a baseball career, a trajectory isn’t necessarily permanent, and one data point is only one data point. Baseball is complicated and baseball players are complicated. We really shouldn’t be surprised when careers are complicated, too.

Thanks to Andrew Koo for research assistance.