Sandy Leon isn’t the best hitter in baseball, but if you set the plate-appearance minimum low enough, then he shows up as the big-league leader in wRC+. He steadfastly refuses to cool off, and so far he has saved the Red Sox behind the plate. It’s a heck of a story.

Mike Zunino isn’t the best hitter in baseball, but if you set the plate-appearance minimum even lower, then he shows up as the big-league leader in wRC+. Maybe that’s not fair to Leon, but then, lowering the threshold for Leon isn’t fair to everyone else. Zunino was brought up for good about a month ago in order to bump Chris Iannetta, and he’s helped to fuel a Mariner surge in the standings. Given what Zunino had been through before, it’s a heck of a story, as well. Zunino is but 25 years old, yet he’s already been to baseball hell.

The story began, perhaps, as something out of baseball heaven. Zunino was the third overall pick in 2012. A year later, he was a regular in the major leagues. The ascent was exciting, the kind of thing a young player dreams of, but Zunino was moved along too quickly. His defensive work was outstanding. His attitude was positive. His offensive vulnerabilities were exposed. His game became occasional power and nothing else, and Zunino saw his OBP drop from .290 as a rookie to .230 as a junior. As the strikeouts soared, Zunino’s stock cratered. He was demoted to Triple-A in 2015. He played a big role in the Mariners having one of the worst team groups of catchers in recent baseball history.

When the new front office was installed, Zunino was deemed a project. He wasn’t given a big-league opportunity. That was something he’d have to earn, through success in the PCL. The organization worked to tweak Zunino’s swing. It worked to tweak Zunino’s approach, and his confidence. Importantly, it also worked to consistently deliver to Zunino one single message. One of the criticisms of the previous regime was that different team officials would say different things to the same player. It’s not necessarily why Zunino struggled so much, but it couldn’t have helped, with Zunino trying to please too many people.

Zunino put in the work, re-establishing himself in the minors. He improved his approach and contact rate, getting the development time he didn’t have before, and by July, he was back with Seattle. The Mariners said Zunino wouldn’t stick around if he didn’t play enough, and in order to play enough, he’d have to perform. He’s been performing.

Zunino has already homered nine times in 91 trips. It’s not surprising to see him go deep — even at his worst, Zunino could put a charge in a ball. But Zunino as an overall hitter has simply been more balanced. The samples are way too small, but he’s sitting on what would be a career-high walk rate and a career-low strikeout rate. To put that visually:

If that were to sustain, Zunino would be a major success. If the new front office has made anything clear from Day One, it’s that it prioritizes strike-zone control. As a major leaguer before, Zunino just didn’t have it. He slumped, and he spiraled. He’s showing encouraging progress now, building off work done a level below. He isn’t “fixed.” He can’t be considered fixed, not so soon. That takes time, and struggles, to see if all the gains stick. But Zunino is now on the right road. He just has to make the proper turns.

Zunino’s approach definitely appears to have matured. Pulling from Baseball Savant, Zunino has lowered his rate of swings out of the zone when behind in the count. With two strikes, specifically, Zunino has maintained his swing rate in the zone, but out of the zone, he’s lowered his rate more than 10 percentage points. As hard as it is to believe, Zunino’s two-strike chase rate is among the lowest in the game. It’s early, but it’s something. Last year with two strikes, Zunino had 11 times as many strikeouts as walks. This year’s ratio is 4.4. Last year, after falling behind 0-and-1, Zunino put up a .461 OPS. This year he’s at 1.062. Zunino now isn’t bailing on at-bats. He’s tougher to put away, giving his power a better chance to show up.

There’s a lot that’s been going on here. If you talk to Zunino, or the Mariners, they’ll mention the importance of being confident. Without question, a confident hitter will do better than a less confident hitter. And, without question, we don’t have any confidence metrics. But ultimately, things do come down to hitting mechanics. Confidence and frustration and whatnot simply determine mechanical consistency. Zunino has probably attempted more adjustments than I can count, but I want to point to one thing in particular. Zunino is showing better judgment, right? Here’s an extra-base hit from 2015:

Here’s an extra-base hit from the other day:

It’s just two swings, but keep an eye on Zunino’s front leg. There’s something subtle there, but potentially quite meaningful. Here are some screenshots, with red lines showing the approximate locations of Zunino’s heel.

A year ago, Zunino was more likely to step forward. He’d pull his front foot back, then he’d thrust it back out again. That could cause Zunino to over-commit, or to commit too early, with his momentum shifting. He could still do plenty of damage to a pitch to left or left-center, but it would be tough for Zunino to adjust. Looking on the right side, Zunino’s front foot is much more up and down. That step is basically eliminated, with Zunino starting a little wider, and that could help Zunino keep his weight on his back leg a little longer. That’s where a lot of plate discipline comes from. We always talk about hitters’ eyes, but that’s only part of it. They have to be able to adjust their swings. It helps to see the ball for an extra split-second. It seems like Zunino now has that split-second, and he’s hitting better than he ever has.

Which is incredible. I wrote yesterday about how I like Keon Broxton because, despite the strikeouts, he blends power with speed and defense at a premium position. Zunino doesn’t run like Keon Broxton — Zunino doesn’t run like Jonathan Broxton — but he’s a quality defensive catcher, meaning he needs to hit only so much. The bar is set low, and Zunino is easily clearing it. He’s always going to have some swings and misses, because of his aggressively vertical swing path, but Zunino with a sound approach is a regular catcher who can slug somewhere between .450 and .500. That’s a valuable player. That’s a long-term core asset.

There could be lessons in here about how to develop a prospect. There could be lessons in here about when it’s appropriate to consider a player a bust. Zunino was taken one pick after Byron Buxton. Buxton’s having his own miserable experience, but he could come out of it one day, too. You have to be patient with the talented ones. And we still have to be differently patient with Mike Zunino now — we need to see this approach sustain a while longer. We need to see it sustain through some kind of extended slump. It’s the slumps that can kill the progress. But Mike Zunino has made progress. He’s been an everyday big-league catcher before. Now he might be becoming a good one.