Last week, Sam Miller wrote an excellent piece for ESPN on the rise of the height-challenged slugger.

But height has always been an advantage in baseball, particularly when it comes to power hitting. The average American male is 5-foot-10, but in the first year of this decade only one of the top 75 home run hitters in baseball was actually listed at that height or shorter. (Six were under 6 feet, and 30 were 6-3 or taller.) The correlation between isolated power and height that year was .46. If Veeck’s right that a shorter game is a more democratic one, baseball has been trending in the right direction: down. Last year saw the weakest correlation (.28) between power and height since at least 1988. The Padres’ Ryan Schimpf led baseball in isolated power after making his debut in June. He’s 5-foot-9 and hit 20 homers. He was joined on the power leaderboards by Mookie Betts (5-9, 31), Rougned Odor (5-11, 33), Brian Dozier (5-11, 42) and Jose Altuve (5-6, 24), among others. There were more batters under 6 feet who hit at least 25 homers than there were batters taller than 6-3 who did. One-year flukes happen. But 2015 and 2014 were, at .32, tied for the fourth-weakest correlation over the past 30 years. This season is barely a week old, which means it’s far too soon to speculate, except wildly and irresponsibly, about what it will bring. The correlation between height and power so far this year is .17. Now forget that number until we have a couple of months of data to confirm it.

It’s not news that home runs are trending back upwards, but as Miller’s article demonstrates, this surge is different from the late-90s power boom, which was driven by big-bodied sluggers all going after Roger Maris‘ single season home run record. This home run spike is more about lower-power guys moving up the ladder, and guys who previously just slapped the ball around learning to punish mistakes.

Which brings us to Cesar Hernandez. The Phillies second baseman is listed here at 5-foot-10 and 160 pounds. Coming into this year, he had eight career home runs and an ISO of .080. He was the definition of a slap-hitter, and last year, the Phillies actually benched him in order to get him to stop hitting the ball in the air.

With Hernandez, we kind of triple-team teamed him in batting practice, telling him to keep the ball out of the air,” Mackanin said before the game. The message is for Hernandez is to take advantage of his speed. “Three hundred foot fly balls don’t work,” Mackanin said. “He has to cut his swing down…”

And an even more direct quote here.

Manager Pete Mackanin pulled him aside that day in Minneapolis and delivered a message. “I told him this wasn’t a rest, that he was going to have to change his swing, eliminate the uppercut, or I was going to start playing Whitey (Andres Blanco) more,” Mackanin said. Bench coach/infield guru Larry Bowa delivered a similar message, telling Hernandez, “You’ll be sitting next to me on the bench for the rest of the season if you don’t make changes.” Hernandez responded quickly. “I watched him in batting practice that day and he was hitting down on everything — line drives,” Bowa said.

Hernandez was running a 67 wRC+ when he was benched on June 20th, and then he ran a 134 wRC+ afterwards, and two weeks into this year, he has a 173 wRC+, seemingly continuing the second-half breakout. So, Mackinin and Bowa’s message got through, and the elimination of Hernandez’s upper-cut has turned him into a much better hitter, right?

Well, maybe. But then there’s this.

Cesar Hernandez, Before and After Benching Time BB% K% ISO BABIP GB% Pull% Exit Velo Launch Angle Through June 20th 6% 21% 0.088 0.310 52% 29% 86.2 5.9 After June 20th 14% 17% 0.106 0.399 57% 42% 87.2 6.3 2017 to date 7% 21% 0.269 0.405 49% 43% 88.6 11.4

After being told to get rid of the uppercut from his swing and hit more grounders, Hernandez did hit more balls on the ground. But that shift from 52% to 57% isn’t that dramatic, and doesn’t really seem like the cause of the huge change in results. After all, Hernandez’s post-benching walk rate more than doubled, and he cut his strikeout rate down at the same time, which is a pretty nifty combination. And from a batted ball perspective, the more notable change is that he started pulling the ball with regularity, and changed his batted ball mix when he did go the other way.

Up through June 20th, Hernandez ran a 65 wRC+ on balls hit the other way, which is bad news for a guy who tries to use the whole field. 41% of his opposite-field balls were fly balls, and opposite field fly balls are almost always outs, especially for guys who don’t have much power.

After June 20th, Hernandez ran a 199 wRC+ on balls hit the other way, and only 31% of them were categorized as fly balls, while his line drive rate skyrocketed up to 35%. His average launch angle on balls fielded by the third baseman, shortstop, or left fielder was 8.1 degrees, down slightly from the 9.2 degree average launch angle he posted on opposite-field balls prior to getting told to make significant changes. But, again, a one degree change in launch angle doesn’t seem like it should result in these drastically different results. And the average exit velocity on those balls went from 85 to 86 mph, so again, it’s not like he started crushing everything the other way.

Nor does Hernandez’s strong start to this season really look much at all like his strong finish to last year. The primary thing that looks similar is that he’s still pulling the ball far more than he ever has before, but now he’s pulling the ball in the air with legitimate power.

Hernandez already has three home runs in the first two weeks of this year, halfway to last season’s overall total. He’s posting a lower ground ball rate than he ever has before, and his average launch angle is nearly double what it was last year. The increased pull% and higher launch angle numbers are straight out of the playbook used by guys like Daniel Murphy to increase their power, but also seem to go entirely against what Mackinin and Bowa ordered Hernandez to do last summer.

After all, they told him to lose the uppercut in his swing or else he wouldn’t play. Here’s the home run he hit against Joe Blanton over the weekend for your viewing pleasure.

I’m no swing expert, but that looks pretty uppercutty to me. And Hernandez’s own comments suggest that his focus for this year was not to be the spray-the-ball-around guy.

This winter, Hernandez, who turns 27 on May 23, added something valuable to his game. He got in the weight room and added 15 pounds of muscle, taking him to 180 pounds. He likes the added strength. “I can hit the ball harder,” the switch-hitting second baseman said.

So far this year, that’s exactly what Hernandez is doing. His exit velocity on balls in the air so far this year is 95.0 mph, up from 91.0 mph last year. An EV of 95 mph in the air puts him in a tie with young slugger Nomar Mazara, and is only half a tick behind teammate Maikel Franco, who is often lauded for his raw strength. His 91 mph EV in the air last year tied him with Peter Bourjos and Leonys Martin. Hernandez bulked up this winter to hit the ball harder, and so far, that’s exactly what he’s doing.

It’s probably worth noting that the Phillies have a new hitting coach this year. Here’s Matt Stairs on his offensive philosophy, from an article back in February.

Stairs has communicated with the Phillies’ front office a few times since he got the job. The Phillies have been building a substantial analytics department, using Statcast™ and other metrics to identify the strengths and weaknesses of hitters. The Phillies are not alone. Teams like the Cubs look at those numbers, and their philosophies have filtered into the clubhouse. Cubs pitcher Jon Lester even told The New York Times last year, “There’s no slug on the ground.” That is where metrics like average exit velocity and average launch angle come into play. “It’s more about certain guys hitting too many ground balls, or why isn’t the ball coming off their bat more solidly when they’re so strong?” Stairs said of those conversations with the front office. “We haven’t gotten too deep into the details, but you have to take baby steps. The biggest thing I’m teaching them right now is [hitting from] left-center to right-center and how to use the top hand when you hit. I think when they start realizing less body, more hands, that’s when the exit velocity jumps.” … Speedsters like Roman Quinn and Cesar Hernandez are other examples. The idea that small, fast players should hit the ball on the ground is antiquated and flat-out wrong, according to Stairs. Ground balls typically equal outs. Line drives are king. “You want to drive the ball through a shortstop or second baseman,” Stairs said. “If I tell Roman Quinn, ‘We don’t want you hitting the ball in the air, we want you hitting ground balls.’ … We don’t want you hitting ground balls. What happens is you start guiding the ball through the zone and you top it and kill the ants and worms in front [of the plate], or you carve it and hit fly balls. “The approach we have this spring is the first two rounds [of batting practice], I want you killing the second baseman and shortstop, up the middle and hard. Don’t think about hitting the ball on the ground. Think about having that good top hand, driving the ball through the infielders on a good line drive. And if you clip it a little bit, now you have gap power.”

So far, Hernandez looks like the perfect example of what Stairs was preaching. Hit the ball harder and get it up enough to get out of the infield, because that’s where production comes from. There’s going to be some contact trade-off — and Hernandez’s contact rate is down a bit this year — but the damage done on contact should provide more overall value than just hitting the ball into the ground and trying to beat out infield singles.

Of course, it’s just two weeks in, and pitchers will adjust if they see Hernandez as more of a threat than he used to be. If he doesn’t cool off soon, the scouting report is going to change; he’s running a .381 wOBA over the 437 PAs he’s gotten since last summer’s benching, so people aren’t going to keep pounding the zone against him just because he’s a little guy forever. And the .400 BABIP he’s put up since he got benched isn’t sustainable, so even if he has figured out how to increase his power, he won’t keep hitting at this level, most likely.

But Hernandez is yet another short guy who has seemingly overcome myth that only big guys can try to hit the ball hard. We might not have any Mark McGwires or Sammy Sosas in this home run revolution, but with guys like Hernandez figuring out how to add some power to their games, this home run spike is much more of a democratic affair.