Aledmys Diaz has already done one thing that’s hard to do in today’s MLB: emerge as a surprise star.

Now all he needs to do is prove this is for real. 

For the moment, the St. Louis Cardinals‘ rookie shortstop is so much more than a mere stand-in for the injured Jhonny Peralta. He’s hitting .336 with a .937 OPS through his first 43 games. He ranks fifth in the National League in batting average and is outpacing Bryce Harper in adjusted offense.

Diaz isn’t about to get caught up in his numbers. As the 25-year-old Cuba native told Cheryl Rosenberg of the Guardian“If you start thinking about stats, you lose focus.”

But for the rest of us, not dwelling on his stats is out of the question.

After all, they’re the things highlighting Diaz as an emerging star, and he’s more intriguing than the average specimen. In the spirit of Yoenis Cespedes, Yasiel Puig and Jose Abreu, he looks like MLB’s next great Cuban star. In the spirit of Carlos Correa, Francisco Lindor, Xander Bogaerts and fellow rookies Corey Seager and Trevor Story, Diaz also fits in with baseball’s young shortstop revolution.

As recently as a year ago, Diaz didn’t seem likely to find his way into either circle.

He didn’t hit the ground running after the Cardinals signed him to a four-year, $8 million contract in March 2014, batting a good-not-great .273 with a .765 OPS at High-A and Double-A that season. Once he was sitting on a .235 average and .636 OPS early last July, the Cardinals designated him for assignment.

Ever since then, though, Diaz has been on a rampage.

In his final 49 games at Double-A and Triple-A in 2015, Diaz hit .337 with a .986 OPS. He then went on to hit .315 with a .987 OPS in the Arizona Fall League. Add that to what he’s doing this season and your eyes begin to widen as you realize Diaz has been raking for almost a year straight.

“I started feeling more comfortable at home plate, then I started making good contact and having quality at-bats,” Diaz said of his turnaround, per Mark Saxon of “With this sport, it’s always mental.”

The catch is Diaz‘s ability, or lack thereof, on the other side of the ball. Both his 10 errors and his metrics characterize him as a below-average defender. There may be no fixing that, as Baseball Americas book on him said he’s a shaky fit at shortstop at best and not at all a fit at worst.

But as long as you’re performing and looking like a legitimately good hitter, subpar defense becomes that much easier to forgive.

The fact that Diaz has drawn walks in only 5.0 percent of his plate appearances makes it look like he has an aggressive approach, but he doesn’t. Going into Tuesday, his overall swing rate of 45.5 percent and chase rate of 26.7 percent were under the league averages of 45.8 and 28.1, respectively.

With a 9.3 strikeout percentage, Diaz is also one of the hardest hitters in the majors to whiff. And according to Baseball Savant, the average exit velocity on his batted balls at the start of play on Tuesday was 90.6 miles per hour. That was the exact same as Mike Trout and Kris Bryant.

If you want to make a great hitter, a disciplined approach, an ability to put the ball in play and an ability to barrel the ball are the right ingredients to start with. Now all Diaz must do is figure out the one thing that’s gotten him into a spot of trouble recently.

After hitting .423 with a 1.186 OPS in April, Diaz is hitting just .256 with a .714 OPS in May. Some kind of downturn was inevitable after such an incredible start, sure, but there’s more than just natural forces at work with this one.

Though Diaz has maintained the solid approach he had in April, his strikeouts are up and the quality of his contact is down this month:

Pitchers have made life tough for Diaz by giving him fewer strikes to hit. He was seeing 50.8 percent of his pitches in the strike zone in April. In May, that figure has dropped to 46.6 percent.

Pitchers have also been throwing to a specific area. Per Brooks Baseball, they didn’t have a set location pattern against Diaz in April. But in May, they’ve set their target against the righty swinger to low and away:

This makes sense on two levels. This is the obvious way to avoid the damage Diaz did to middle-in pitches in April. This is also the classic way of dealing with dead pull hitters.

Hence, Diaz‘s missing ingredient. The best hitters can use all parts of the field, but he entered Tuesday pulling 48.9 percent of his balls in play. To boot, times in which he’s pulled the ball are generally the only times he’s performed like a great hitter:

  • To Left: 1.581 OPS
  • To Center: .767 OPS
  • To Right: .739 OPS

What Diaz must do now is adjust to the adjustment against him. That’s where there’s good news. He’s trimmed his pull percentage from 52.2 in April to 45.5 in May and upped his use of the opposite field from 16.4 percent to 27.3 percent.

This hasn’t translated to results, but it’s promising that Diaz hasn’t responded to the low-and-away attack by doubling down on his pull habit. That’s a sign he might be capable of cleaning up his big exploitable weakness. 

This is not to be taken as a guarantee he’ll keep hitting .336, but Diaz doesn’t need to be a Miguel Cabrera doppelganger to pull his weight. At a time when the average shortstop is only hitting .254 with a .693 OPS, he has a relatively low bar to clear to qualify as a star-caliber hitter at his position.

Staying above that bar is doable. With nearly two full months of major league action in the bag, it says a lot about the quality of Diaz‘s bat that you really have to dig to find his fatal flaw. And if he does indeed clean that up, there won’t be many question marks left looming over his hitting talent.

To put it in straightforward terms, this guy might actually be for real.


Stats courtesy of and FanGraphs unless otherwise noted/linked.

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