Let’s take a little stroll down the walk leaderboard, shall we? It’s not the most exciting leaderboard on the site, but every board can tell you something. In first we’ve got Joc Pederson. Hell of a rookie season underway. After that we’ve got Bryce Harper. Looks like he’s finally turning that corner. Carlos Santana, Kris Bryant, Matt Holliday — disciplined hitters, all of them. Alex Avila and Jose Bautista are no strangers to the free pass. And then there’s Carlos Peguero. Yes, that Carlos Peguero. If you don’t know him, you’re interested. If you do know him, you’re speechless.

For reference, before this year, Peguero had been in the majors for parts of four seasons. Spent the bulk of that time with the Mariners. He drew eight unintentional walks, in more than 200 trips to the plate. In this year’s early going, he’s batted about a third as much. Still a very small slice of playing time. He’s drawn a dozen unintentional walks. When seen before, Peguero gave off the impression he was clueless. Now he’s having excellent at-bats against Felix Hernandez and Sonny Gray. Also, he is impossibly strong.

Peguero was a familiar kind of player. Big, hulking, elite-level power, no plan in the box. He had it in him to do damage in Triple-A, but he didn’t have an answer to major-league pitching. He’d run comical walk and strikeout numbers, and he’d swing at almost half the pitches out of the zone. There was no mystery why team officials were intrigued, but there was also no mystery when Peguero failed. He was the hitter equivalent of the pitching prospect with the triple-digit fastball. Most of them never find command.

It seems I wrote about Peguero last in January 2014. The title of that post was “When It’s Time to Give Up on a Carlos Peguero.” Discussed the nature of patience when dealing with such impressive raw skills. Late that month, Peguero was purchased by the Royals from the Mariners. About 11 months later, Peguero was released. He joined the Rangers this past January, and now he has a 142 wRC+. He has the same WAR as Alex Gordon.

Pretty obviously, we can’t conclude that Peguero is a great player now. Much more to do, and he still strikes out a bunch. Contact will never be a part of his game. But according to StatCast, he ranks fourth in baseball in average batted-ball velocity. He has one of the very lowest soft-hit rates, and one of the very highest hard-hit rates. Peguero hasn’t sacrificed much in the way of power as he’s learned to take some pitches. What it looks like is something has clicked. That much, we need to discuss. Potential transformations like this are few and far between.

Here’s a very simple graph. Seen, Carlos Peguero’s swing rates, combining Triple-A and the majors. Last year, he spent almost the whole season in the minors. This is an unusual trend:

An average swing rate is about 45%. The first three years here, Peguero was an extremely aggressive swinger. Last season, he calmed down some, showing some patience with Omaha. This year, he’s been even more patient, taking that into the major leagues. Peguero’s swing rate is now percentage points lower than average. It’s lower across the board, in all situations.

Prior to this year, in the majors, Peguero swung at 48% of pitches out of the zone. At the moment he’s at 30%. In terms of out-of-zone swing rate, Peguero has gone from the 0th percentile to the 49th. In terms of overall swing rate, Peguero has gone from the most aggressive 1% to placing in the bottom fifth. Used to be, Peguero showed the swing habits of Pablo Sandoval. Now he looks more like Shin-Soo Choo. There are little changes, and then there are dramatic changes, and we’re unaccustomed to seeing dramatic changes in the area of plate discipline.

And as it happens, there’s something else. We’ll take a look at Peguero’s spray charts. These come from the Interactive Spray Chart Tool. Peguero in the majors, before:

Peguero in the majors, now:

Suddenly there’s almost nothing to the pull half of the field. There are balls hit up the middle, and to the opposite alley. Peguero had up-the-middle power before, but he was a pull hitter, and you can see all those groundballs to first and second base. This is a changed man. This isn’t the Carlos Peguero that two teams gave up on.

So: why? What on earth happened? A clue, via Stefan Stevenson in March:

He’s shown power with a homer and two doubles despite changing to a more compact swing, which has helped improve his plate discipline, Banister said, as his three walks and six strikeouts suggest.

What’s suggested is that Peguero has a quicker, simpler swing. And again, this gets to the relationship between swing mechanics and discipline. If a hitter can cut down his swing, he can buy himself additional milliseconds. If a hitter can keep himself back a split second longer, he won’t be so prone to over-committing early. With Peguero, the evidence is there: the spray charts show he’s hitting the ball more over the plate, instead of in front of it. And the reduced swing rates imply better recognition and fewer early commitments. Peguero isn’t trying to hit the crap out of the ball every time. By simply staying back, he sees pitches longer, and that can make an enormous difference.

That doesn’t mean this is permanent. That’s the tricky part. I mean, nothing in baseball is permanent, but with Peguero in particular, you wonder about sustainability. From Evan Grant in April:

For the first two weeks of the spring training schedule, the Rangers saw a hitter they described as completely changed. Peguero was more willing to take pitches the opposite way and also showed more disciplined. But after going 3 for 4 against his former Seattle teammates on March 22, things went downhill. He finished the spring in a 5 for 24 funk that included 13 strikeouts.

…

“I just have to try not to do too much,” Peguero said. “Maybe it was some timing. Maybe I got a little impatient.”

Peguero, in spring, came out of his discipline, once more winding up over-aggressive. And this is nothing new for him. Ryan Divish has covered the Mariners for years, and he also has a history covering Tacoma. He says that Peguero was always a project, and sometimes it looked like he was making legitimate progress staying back and compact. Peguero was known for his impressive batting-practice displays, and there were times that he’d resemble more of a complete hitter. But then he’d revert to old muscle memory in pressure situations, especially with men on base. He’d try to do too much, and he’d try to hit the ball too hard, and that’s not the hitter the team was trying to make him into. It wasn’t a matter of intelligence, or bad eyes; the Mariners just couldn’t get Peguero re-programmed. The lessons didn’t stick.

To this point with the Rangers, the lessons have stuck. It’s to be seen if they remain that way, but Peguero, to his credit, also has a more mature perspective:

“I’m able to have a plan, a purpose in my life, understand what my type of game is. Don’t get out of my game,” he said. “If [pitchers] throw it away, don’t try to pull it, just go with it. Understand what they’re trying to do with me and what kind of pitch they use to try to get me out.”

It’s easy to talk about the things you want to be able to do. For the first time in the majors, though, Peguero is actually doing them. Which means that maybe, just maybe, the lessons are internalized. Maybe Peguero has now been re-programmed to understand that while hitting the ball 500 feet is amazing, 400 feet is plenty. The signs right now are encouraging, in a way we never could’ve imagined. Shortly, the Texas Rangers are going to welcome back Josh Hamilton. But he might not be the best outfielder on the team.