Beginning last season, there’s been a raging debate concerning the identity of baseball’s best shortstop. In fairness, I guess, people have probably been arguing about this forever, but now there’s this outstanding, new, young crop, and it’s hard to believe they all exist. There are veterans in there like Troy Tulowitzki and Brandon Crawford, but you’ve also got Carlos Correa. There’s Francisco Lindor, and there’s Xander Bogaerts. Corey Seager! And maybe we’re supposed to include Manny Machado. There are so many good shortstops. There are so many good shortstops that I’ve left several out.

I’m very comfortable asserting this: Whoever might be the best shortstop in baseball, I believe it is not Aledmys Diaz. Diaz isn’t a premium baserunner, nor is he a premium defender. Remember, he wasn’t even supposed to be in the majors. But here’s a fact for you — Machado leads all players listed as shortstops in wRC+. There in second place, trailing by just five points, is Diaz. He leads everybody else. And he’s officially now a National League All-Star.

It comes off like a classic case of the Cardinals. In the middle of last summer, when Diaz was in the minors, he was removed from the 40-man roster. Anyone, at that point, could’ve had him. The Cardinals brought him back. The rest is history, and the present.

The door was opened when Jhonny Peralta got hurt, and at that point in March, I wrote that the Cardinals should give Diaz a chance. The whole argument was basically “Diaz just had an awesome second half,” and there wasn’t much else on the market, but I didn’t think Diaz would do this. No one thought Diaz would do this. We had him projected for a sub-.300 wOBA. Here’s a little table, showing the five players who are currently beating their preseason projected wOBAs by the most:

They’re all surprises. Maybe I should be writing about Ramos. But Ramos, at least, had hit in the majors before. Same with Altuve, and same with Ortiz. Lamb at one point destroyed minor-league competition. Diaz had a half-season of offense. I figured he could do better than .294, but his productivity to date has been unreal. And what I love most: Diaz had his hot start, and then he slumped. It’s not an unusual pattern for a low-profile rookie. But Diaz has adjusted back. In that way, he’s passed the biggest test. Early, he succeeded as an unknown. Now he’s succeeding as a known.

I’ll get into the adjustments, but first I’ll note that, overall, Diaz has made 85% contact. Right away, you can tell he’s a shortstop with bat control. And according to Statcast, he’s pretty average in terms of batted-ball speed on flies and liners. He ranks right by names like Kyle Seager, Adrian Beltre, Robinson Cano, and Mookie Betts. Diaz isn’t going to be an all-fields power hitter, but he’s proven his power to the pull side. That part of his game isn’t a fluke. Now then, it’s time for some rolling averages. I think this is the best way to tell the story of Diaz’s season. Why not start with his overall offense?

Diaz’s first month was absolutely insane. He was on nobody’s radar, and he took advantage of that. The inevitable slump followed, and you can see that Diaz reached some fairly low depths. But over the past few weeks, he’s crept back up. That’s him adjusting to the adjustments. That’s him reacting to opponents developing a plan. This, right here, is the overall trend. Below are just more details.

Like, the power. Unsurprisingly, Diaz’s power has followed the same pattern as his production. The two are inextricably linked, but you see the same peaks and the same valley.

It’s remarkable for any shortstop to run an ISO north of .200. It’s not like Diaz is being driven by a sky-high BABIP. So, the power: For the most part, it’s to left and left-center. When that’s the case, you can see players fall in love with themselves and over-pull. But, take a look — Diaz has done well to increasingly use the whole field. It’s something opponents have forced him to do, but not every player can do it.

Still a few more left to go, and they’re all related to one another. In April, Diaz struck out just four times, somehow. In the following month, that number jumped up to 17. The first one was never going to be sustainable, but Diaz hasn’t allowed the strikeouts to spiral. They’ve since stabilized, if not come back down.

Remember that a league-average strikeout rate is around 20%. Diaz seems to want to be between 10 – 15%, which would be excellent for a player with selective power. We continue! Pitchers have noticed Diaz’s potency. After being aggressive early, they’ve tried to get him to chase.

Again, nothing unusual. Diaz was a nobody, then he smacked some dingers. Major leaguers have investigated whether Diaz might have a familiar tendency to chase. Lots of minor-league nobodies chase. It’s what causes them to wash out of the bigs. Yet Diaz has discipline, or restraint, or whatever. What’s the best way to respond to getting pitched out of the zone? Just let them pitch you out of the zone.

In April, Diaz drew three unintentional walks. In May, he drew four. In June and July combined, he’s drawn 15. So now he looks like a player with bat control, discipline, and pop. For a little stretch there, Diaz got exposed off the plate away, but, most right-handed hitters go through that. Diaz has since focused on attacking pitches in or over the middle. He’s spit on more of the away pitches, and pitchers, in turn, have begun to work Diaz more inside, recognizing that he’s cleaned up his approach.

Of course, Diaz isn’t a finished product, and of course, this isn’t it. Opponents aren’t done trying to figure him out, and Diaz isn’t done reacting to them. There will be future slumps, just as there will be future hot streaks. But the way I see it, the first big hurdle is reaching the majors in the first place. And then the second hurdle is achieving success, after succeeding initially. Granted, initial success might be considered a hurdle all its own. Just ask Byron Buxton. But organizations always want to see how their players respond to failure. Diaz responded to failure in the minors by beating the crap out of the ball, and Diaz has responded to failure in the majors by adjusting, taking pitches, and hitting well again. It doesn’t mean he’s a lock to be a quality, long-term shortstop. You just have to like the odds. Certainly, more than you used to. It has to be said that the Cardinals have done it again.