It doesn't take much with the bat for Billy Hamilton to be a great player. He's a world-class defensive center fielder. Of course, he's a world-class baserunner. Just between his defense and baserunning, Hamilton can be worth up to three Wins Above Replacement without adding anything at the plate, and the list of Major League players with that kind of ability is a short one.
Problem is, Hamilton has not only added nothing at the plate, he's subtracted, and last year he took those subtractions to a nearly unbearable level. Hamilton was one of the worst hitters in 2015 with a 52 wRC+ that's either right at or perhaps even below the lowest acceptable level for any hitter, regardless of what other contributions he offers. Hamilton was teetering on the verge of wasting his preternatural athletic abilities due to what he could (or rather couldn't) do at the plate.
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And the fix has seemingly been so simple. Hamilton himself has mentioned it in consecutive offseasons. So has his coaching staff. Jeff Sullivan first wrote about it two springs ago. The fix: fewer fly balls. While players with similar skill sets as Hamilton -- such as Ben Revere, Dee Gordon, Norichika Aoki and Elvis Andrus -- were taking advantage of their strengths by chopping the ball into the ground and legging it out, Hamilton was at odds with his own assets by hitting the ball in the air more than some sluggers.
When I followed up on this phenomena earlier this spring, though, I found that Hamilton's problem wasn't just the fly balls; the ground balls were an issue, too. Hamilton's BABIP on grounders in 2015 was confoundingly only league average, and so was his overall production. It's possible Hamilton just ran into some tough luck, but I also found some evidence to suggest that Hamilton just didn't hit good enough grounders to ever make it through the infield with any real frequency. Infield hits can only take you so far.
This year, Hamilton is back to hitting enough to be a more-than-useful player. With an 86 wRC+, Hamilton can easily be a three-win or better type of guy -- an above-average center fielder. And it looks like he might finally be employing the obvious fix.
In his first two full seasons, Hamilton put the ball on the ground 42 percent of the time, or roughly as often as his slugging teammate Jay Bruce. This year, he's cracked the 50 percent threshold. You'd probably still like to see it go higher, but from last year to this year, Hamilton has one of the largest increases in ground-ball rate. For a batter like Adrian Gonzalez, who has baseball's highest increase in ground-ball rate, that's not a good thing. For Hamilton, it's perfectly according to plan.

And the production on those extra grounders?
Hamilton, ground-ball production
2013-15: .272 BABIP, 54 wRC+
2016: .344 BABIP, 121 wRC+
In 2016, Hamilton has been among the most productive ground-ball hitters in baseball. The BABIP makes more sense, for someone with Hamilton's speed. He never should've been a league-average hitter on grounders. At least it didn't feel like it. This version of Hamilton is much easier to understand.
But then there's this: Over the past 10 seasons, only eight qualified hitters have finished a season with a ground-ball wRC+ north of 100. No one's topped 119. Hamilton's number is bound to regress. And if you're wondering how this regression might manifest itself, look no further than where Hamilton is baseball's biggest outlier:
Isolated slugging percentage, ground balls
1. Hamilton, .148
2. Kevin Pillar, .057
3. Jose Altuve, .057
4. Brian Dozier, .056
5. Trayce Thompson, .055
Hamilton has nearly three times the ISO of the guy in second place. Overall, Hamilton has hit for as much "power" on ground balls this year as Jose Abreu. Hamilton's ground-ball ISO is the same as Mike Trout's line-drive ISO.
Of course, Hamilton is more equipped to turn ground balls into extra bases than anyone. The thinking behind getting Hamilton to trade some of his air balls for ground balls wasn't only that Hamilton's air balls were weak and harmless, but that Hamilton's ground balls could have unprecedented value, because he can do this with them:
Gif: Billy Hamilton double and clapping
There's also evidence that Hamilton might just be hitting better grounders. Last year, Hamilton's grounders were weak. I found that roughly 11 percent of them got through the infield, whereas a similar slap-hitting speedster like Dee Gordon shot closer to 20 percent of his grounders into the outfield. This year, Hamilton's hard-hit rate on grounders is up, and plenty more of them are getting through the holes ...

... affording him more opportunities to take advantage of his speed ...
Gif: Hamilton legs out a double
... as well as the outfield shifting teams have begun implementing on him due to his opposite-field air-ball tendencies:
Gif: Hamilton races to third
That being said, just like with the wRC+ disclaimer, the outlier ISO figure understandably comes with a disclaimer as well. If Hamilton finishes the season with a ground-ball ISO of even .100, he'll be the first to do so. Over the past decade, fewer than three players per year have clocked in north of .050, and the highest ground-ball ISO on record is Carlos Gomez's .078 mark in 2013. Hamilton has the tools to do this better than anyone, but he's also certainly been fortunate, and now has some regressing to do.
But surely none of this can be viewed as a bad thing for Hamilton. He still can't seem to figure out those pesky bunts for whatever reason, but after two years of a maddeningly fly-ball-heavy approach, Hamilton is finally showing signs of adjusting. More than half his balls in play have been grounders, something he's never come close to doing for this long of a stretch before. Not only more grounders, but better grounders -- the type of grounders hit hard enough to squeak through the infield and really let Hamilton take advantage of his speed. And what's better than Hamilton being able to take advantage of his speed?
A version of this article first appeared at FanGraphs.com. This story was not subject to the approval of Major League Baseball or its clubs.