The player with baseball’s third-best wOBA started on Tuesday, and the first time he came up, he drilled a low-away curveball into center for a single. The next time, behind 0-and-2, he fought off an inside fastball and lifted another single into center. The third time, he yanked a low slider down the left-field line for extra bases. I’m taking a risk by writing this post before the game is fully over, so perhaps there’ll be a fourth time, and maybe that’ll go well and maybe it won’t. No matter the outcome, it’s hardly the most important data point.

The most important data point is this: Right now, the best hitter in baseball has been either Mike Trout or Troy Tulowitzki. To round out the top five, you’ve got a selection, including names like Andrew McCutchen, Edwin Encarnacion, and Devin Mesoraco. Four of these players named are known to be amazing. Mesoraco’s been amazing; he’s just not known for it yet.

And in fairness, you’re talking about just a little more than 300 plate appearances. I do get it, in a way, and Mesoraco’s track record doesn’t support the numbers he’s been posting this summer. But that’s precisely what makes this so exciting. Mesoraco has been a top prospect, and in his early stages, he struggled to hit with any consistency. He turned 26 in the middle of June, and he’s basically more than doubled his offense. Given what the Cincinnati Reds have been through, you might wonder how they’ve managed to hang around in the race. Mesoraco isn’t the whole reason, but he’s more of a reason than anyone would’ve guessed.

It’s time for the Historical Perspective Game. A year ago, Mesoraco batted 352 times and posted a 74 wRC+. At this writing, he’s batted 312 times and posted a 165 wRC+. That’s a wRC+ improvement of 91 points. If the season were to end today, where would that rank among the biggest season-to-season improvements? Let’s set convenient minimums of 300 plate appearances in consecutive years. That yields a pool of 13,352 player-season pairs since 1920. Here are the top 12 biggest wRC+ gains:

There’s current Devin Mesoraco, in second place. His improvement is almost unprecedented. And, look at the names around him. Lopez had hit well before, and he did this in his 30s. Hamilton had hit well before. Ramirez had hit well before, and Ruth had obviously hit very well before. Pendleton peaked. Kaline broke out as a youngster. Your eyes might be drawn to Beltre, who followed up his breakthrough season by disappointing with the bat in Seattle. But once he got out of Safeco he was re-revealed to be an upper-tier slugger, so that’s not as black-and-white as it seems. And anyway, to get back to the start of this paragraph, Mesoraco didn’t have a track record before the 2014 eruption. The hope wasn’t that he’d build on what he’d done before; the hope was that he’d cash in some of his prospect hype.

Eight catcher seasons in history have achieved at least a 165 wRC+ over at least 300 plate appearances. Mike Piazza’s responsible for three of them. Buster Posey has topped out at 164. For his position, Mesoraco is having one of the better offensive seasons ever. Of course, we still have to let this season play out, but Mesoraco’s worst month so far has generated a 129 wRC+ and a near-.500 slugging percentage. He’s cooled down from his start, but he’s cooled to a superstar level.

So what’s the Mesoraco improvement story? Eno asked him a month and a half ago, and Mesoraco talked about some swing changes. He’s also just gotten more familiar with playing in the major leagues, and he’s one of those bits of evidence that catchers blossom a little later than non-catchers. You can see hints of an adjusted swing in Mesoraco’s follow-through:

You can also see them in his statistics:

Stat 2011-2013 2014 ISO 0.134 0.287 BABIP 0.248 0.340 GB% 45% 34% Contact% 81% 70% 1stSwing% 39% 26% Pull wRC+ 154 327

Mesoraco has been baseball’s most productive pull hitter. He’s putting the ball in the air more often, and he’s making contact less often, but he’s hitting the ball a hell of a lot harder, which is obviously doing more good than bad. He’s been less aggressive with the first pitch, which suggests a change to approach along with the change to his swing. While one probably shouldn’t believe that Mesoraco is really this good, there are plenty of reasons to think he’s significantly different from what he was a year ago. The Reds were hoping for improvement. They never would’ve dreamed of this much, and now Mesoraco looks like a genuine slugger at a defense-first position. His defense, also, isn’t bad.

As I wrap this up, Mesoraco just popped out to the backstop. His wRC+ is down to 164, which changes a few of the numbers above. You can focus on that little tiny detail, or you can step back and admire the whole incredible picture. Devin Mesoraco has taken a step forward for the Reds. How much of a step forward? He’s had one of the very biggest season-to-season offensive improvements of all time. And there’s been a lot of time. There have been a lot of players. Mesoraco’s been breaking out for a while, and the only thing left is for people to notice.