Sunday afternoon, Domonic Brown did something he’s been doing a lot of lately. Brown faced Mike Fiers in the bottom of the first, with two on and two out. After a first-pitch curveball found the zone, Fiers missed three straight times, with a heater and a couple changeups. Brown scooted up in the box, and Fiers came inside with a cutter, or a slider, as if that detail’s important. Brown saw it, swung at it, and blasted it, way out to right field for a three-run dinger. It was Brown’s 14th home run in 32 starts. It was his 16th home run of the season. Brown is the National League leader in that category, after a spring in which people were concerned he might not find enough playing time.

Sunday afternoon, Domonic Brown did something he hadn’t done for a while. Brown faced Tom Gorzelanny in the bottom of the seventh, with one on and two out. After a first-pitch slider found the zone, Gorzelanny missed three straight times, with a slider and a couple heaters. The 3-and-1 pitch was a fastball that Brown went after and tipped for a strike. The next and final pitch was a slider that just missed, a little low and a little away. Brown watched it, and Brown walked — unintentionally — for the first time since April 30. Brown had just walked the day before, too, but that one was done on purpose.

It’s June, now, but it’s crazy what Brown managed to accomplish in May. No one in baseball hit more home runs than Brown’s 12. Only three players beat Brown’s slugging percentage of .688, and two players beat Brown’s isolated slugging percentage of .385. Brown also didn’t walk once. Only Endy Chavez and David Adams also didn’t walk once in May among regulars and semi-regulars, and they batted half as often. And they weren’t good. It’s weird, what Brown pulled off.

Month splits are stupid. Specific month splits are stupider. There’s nothing particular about a month, and there’s definitely nothing particular about May. But what month splits do is allow us to generate helpful trivia. Like this! I looked at the history of Mays, given at least 100 plate appearances. A total of 46 different times, someone has hit at least a dozen home runs in May. In Brown’s May, he didn’t walk one time. The next-lowest walk total among those dinger-hitters is six, by Ryan Howard (2006) and Bing Miller (1922). Meanwhile, there have been 12 Mays in which a player didn’t walk once over at least 100 plate appearances. In Brown’s May, he slugged 12 dingers. The next-highest dinger total among those non-walkers is five, by Carlos Baerga (1994). Domonic Brown had an unusual month, and it leaves us somewhat perplexed. Excited but perplexed.

Home runs, of course, are more important than walks. When a player’s hitting home runs like Brown has been, it doesn’t make sense to be critical of his walk total, because that’s just being critical for criticism’s sake. Brown hadn’t hit for this kind of power before, and it seems like he’s beginning to achieve his considerable potential. That’s the exciting part. But the walks matter because they’re indicative of a potentially unsustainable approach. Phillies fans don’t want Brown to be productive for a month. They want him to become the player he was supposed to become, and so one has to wonder what’s up. How is Brown doing this, and what’s going to come next?

If you ask Brown, or a lot of other people, you’ll hear that Brown’s finally getting a chance to play every day. It’s true that he’s been kind of jerked around in the past, which is probably unhelpful for the development of a top prospect. Now Brown’s getting comfortable in the bigs, and he’s starting to hit like it. The explanation is just that simple. But what does that comfort mean? Where does it show up in the performance numbers, besides just the results?

As always, we can show correlations without demonstrating causation. But Brown’s power success has come with an adjustment in approach. He’s changed himself to become more aggressive, and this table will show how:

Split O-Swing% Z-Swing% Contact% Zone% BB% K% wRC+ 2010-2012 28% 68% 81% 46% 10% 19% 90 Apr-13 29% 69% 80% 45% 9% 18% 84 May-13 36% 77% 81% 50% 0% 19% 172

In May, Brown swung a lot more often than he used to. Maybe that much is obvious, just given that he didn’t draw a walk. Here’s another sampling of data, showing ten-game rolling Z-Swing% averages:

In the first half of May, Brown hit four homers. In the second half, he hit eight, and you can see a corresponding rise in his rate of swings at strikes. Brown says he’s more prepared to hit early-count fastballs, and the data supports the idea that Brown’s been more aggressive at the plate, generating encouraging results. He’s swung at more strikes, and while he’s also swung at a few more balls, he hasn’t been hacking. He’s been hitting, in the classic sense.

Now, used to be that people liked Brown in part for his ability to draw frequent walks. So there’s some measure of concern that Brown went a whole month without a single one. But there’s no such thing as an ideal, single batting approach. Previously, the more patient Brown under-achieved. The newer, more aggressive Brown has found success, and that’s what’s most important. The idea isn’t to make prospects succeed a certain way. It’s to make prospects succeed. Brown’s finally doing that.

He’s swung in 16 of 20 3-and-1 counts. Before this year, he swung in 29 of 53. He’s swung in four of 14 3-and-0 counts. Before this year, he swung in three of 23. And here’s the thing: pitchers will adjust to the new Domonic Brown. They’ll pitch him differently, and more carefully, and then there will be a greater number of walk opportunities. If Brown proves that he’s dangerous, he’ll get pitched around more. As he gets pitched around more, he should walk more. Walks can follow power, more than power can follow walks.

But that’s going to require an adjustment from Brown, too. A simple idea of plate discipline is swinging at strikes and laying off balls. A better idea is swinging well at the right strikes, and laying off the rest. Brown — now more aggressive — has hit for power, but he’s hit for a very certain kind of power. From the ESPN Home Run Tracker:

Brown’s been aggressively trying to pull the ball. He’s been looking for fastballs early in counts. Oftentimes, hittable pitches have been there, allowing Brown to have his success. There are now probably going to be more plate appearances when Brown doesn’t get the pitch he’s looking for. The challenge will be still getting something out of those plate appearances, whether it be walks or base hits. It’s going to be a time for controlled aggressiveness, and that might well be Brown’s final test.

Brown knows he’s going to be pitched differently, but that’s going to happen because he’s earned it. Baseball is a game that’s just constantly adjusting, in both directions, and Brown’s made an adjustment that’s gotten him closer to breaking through. Perhaps as a consequence of playing every day, Brown learned to go up to the plate with a different idea. Now pitchers are going to have a different idea, and we’ll see if Brown’s able to blend both power and walks. That’s the destination. Not a certain amount of power, or a certain amount of walks — appropriate amounts, based on what Brown’s given.

Dustin Ackley just got demoted by the Mariners, in part because they determined he was too passive at the plate. People loved Ackley’s ability to draw walks. Ackley’s going to have to earn those walks by punishing strikes. Domonic Brown is in the process of taking that step, and there are only so many steps.