It wasn’t too long ago that former Phillies great Ryan Howard was a fixture in MVP discussions, atop league leaderboards and on lists of the game’s most marketable stars. But the slugger’s once-promising career is all but over now, after the Atlanta Braves released him in early May.

On the surface, Howard’s fall doesn’t seem completely atypical of a plodding slugger. But his abrupt decline had less to do with aging or ineffectiveness than it did a specific tactic sweeping through baseball during the back half of his career. The defensive shift ended Howard’s career, and it might have cost him a shot at the Hall of Fame as well.

When the shift is on, defenders move from one side of the infield to the other to give themselves a better chance at cutting off batted balls from hitters who consistently drive the ball in one direction. Howard was a great candidate for the maneuver because he pulled groundballs 66.5 percent of the time, compared to this year’s league average of 53.8. While some hitters try to overcome the shift with well-timed bunts or tactical changes, Howard always stubbornly refused. “All you can do is continue to swing,” Howard said in a 2015 interview with MLB.com.

NO SHIFT SHIFT Batting average .424 .282 Average SLG .553 .361 Average wRC+ 162 71 Runs above average +17.1 -52.4 Ryan Howard with and without the shift, 2010-16 Runs above average totals all the runs a player’s hitting generated relative to an average player who had the same number of plate appearances. Shift data is tracked only on balls in play. Source: Fangraphs

That stubbornness proved to be Howard’s downfall. Against the shift, Howard posted a batting average of .282 and slugged .361, good for a weighted runs created plus that was 29 percent worse than average. When he wasn’t staring down the shift, Howard was a fearsome hitter with a .424 batting average, a .553 slugging percentage and a wRC+ 62 percent better than average (that wRC+ is identical to the one he posted in 2006, his MVP year).

The trouble for Howard was that the no-shift version of him seldom got a chance to shine, because teams almost always shifted against him. From 2010 (the first year for which we have shift data) to 2016, Howard had only 224 plate appearances where he did not face the shift, compared to 1699 with it on. Every team that adopted the shift started off by employing it against big, slow, pull-happy hitters like Howard. As a result, Howard saw more shifts than anyone except David Ortiz, another hitter with the same weaknesses.

Ortiz made an effort to adapt; Howard kept plugging away the way he always had. In the first eight years of his MLB career, Howard produced 21.6 wins above replacement. Over his final five seasons — a period during which use of the defensive shift increased exponentially — Howard was worth an astonishing 2.2 wins below replacement. Injuries also limited his productivity, but even when he was healthy, he was ineffective. As a slow, defensively-challenged first baseman, he relied on his bat to be useful. When the shift neutralized Howard’s hitting, he lost his value to a major league roster.

We can never know the true toll the shift exacted on Howard’s production, but we can estimate it: I asked the makers of a simulation game called Out Of The Park Baseball to create a version of MLB without the shift. (Just imagine a universe in which baseball commissioner Rob Manfred managed to outlaw the tactic.) Then I had them replay Howard’s career three times, starting from 2009, to get a range of outcomes for his final résumé.

In a league without shifts, Howard is a completely different player. In the three simulations, Howard finished with an average career batting line of .272/.355/.527, far better than his actual career numbers of .258/.343/.515. Of course, league-wide run-scoring is generally a bit higher in the shift-free game, but even after adjusting for a higher offensive baseline, Howard racked up an on-base plus slugging percentage that was 40 percent better than league average. In the simulations, that offensive production won him between one and five more All-Star selections.

In this world, Howard’s gaudy offensive stats and numerous league-leading totals make him a bona fide Hall of Fame candidate. In order to estimate his chances, I used the same logistic regression model I employed to look at David Ortiz’s case last year, using a player’s Jaffe WAR Score system (JAWS) rating to predict his odds of Hall of Fame induction. Each of the three hypothetical Howards had between a 10 and 55 percent chance of achieving baseball’s highest honor:

So even in a world without the shift, Howard was hardly a lock for Cooperstown. But like Ortiz, he could have benefited from some hallmark achievements and postseason success. For example, in one of the simulations, Howard hit 547 homers — only 10 first basemen have ever passed the 500 home run mark, and seven of them are either already in the Hall or likely to make it there. In that same universe, Howard’s Phillies won two more championships as he racked up multiple playoff series MVPs, no doubt earning a reputation as a postseason hero. In that world, it’s hard to imagine how Howard doesn’t make the Hall of Fame.

Nothing is certain in baseball, not even in simulations of it. Without the shift, maybe Howard’s knees would still have given out, or maybe pitchers would have found another way to frustrate him. (Then again, maybe not having to worry about the shift would free Howard up to improve his offense even more, allowing him to finish his career more like Jim Thome or David Ortiz.) Either way, a world without the newest defensive tactics would have at least given the big slugger a chance at Cooperstown, which is more than most players can boast.

But although Howard succumbed to the shift, his demise also tells us about the future of the tactic — and why its effectiveness might eventually tail off. When modern teams first started realigning the infield, there were plenty of obvious candidates who would be vulnerable to its effects. But as players like Howard get pushed out of the league by the shift, there will be fewer and fewer hitters on whom it can be used so effectively. Eventually, the rewards of slick defensive positioning will shrink; like most tactics in baseball, the shift will have diminishing returns.

Had Howard’s career started a decade later, he might have had to cope with the shift in the minors and found a way to adapt. As it was, he came up as the shift was rising, and it probably cost him a long career and a chance at the Hall of Fame.

CLARIFICATION (June 6, 6:20 p.m.): Shift data is tracked only on balls in play. The table has been updated to include this information, which was previously omitted.