Aledmys Diaz asks for ABs

Alessandro Zilio
9 min readMay 16, 2021

The Astros season has been somewhat of a rollercoaster: after a 6–1 start the team went on a skid, due to bad performances and a bout of COVID on several key players, so that they relinquished the division lead to the surprising Oakland Athletics and visited the scary under-.500 zone.

That was just a momentary blink though: the Houston bats heated up again and the pitching, hurt by a Jake Odorizzi injury, found unexpected results in Luis Garcia and Kent Emanuel, that, along with solid yet unspectacular outings by Zack Greinke and Cristian Javier, and a Lance McCullers Jr. on a roll, brought the team back up 5 games over, still behind the A’s but closer to the top.

The bullpen is still wavering, with the law firm Ryan (Pressly) and Ryne (Stanek) as the sole surefire arms to call for late in the game, waiting for Enoli Paredes to return and riding a great Andre Scrubb as of late.

Lineup-wise there’s not much fault to be found: Altuve, Brantley and Bregman are their solid selves, Yuli Gurriel is still walking and hitting like a top 1B in the league and Yordan Alvarez is…historical! Even the bottom of the lineup, with Kyle Tucker finally pulling the ball and Martin Maldonado not swinging at everything, is getting into the act.

There’s a guy though that, as for his underlying stats, is one of the best bats in the Astros roster and he’s getting few and scattered ABs, starting games when one of the stone-setted 1 to 9 guys in the lineup gets a day off or pinch-hitting when in need.

Such is the life of a utilityman, Aledmys Diaz!

Raise your hand if you had Diaz as one of the best Astros hitters a month into the season…no one? Well that’s no surprise, although Aledmys is far from breaking news at this point of his career.

He was a surprise way back in 2016 when he debuted for the St.Louis Cardinals, one of the many good but unheralded prospects the Cards seem to find every other day in pure “Cardinal black magic” way. After a long stretch between AA and AAA, being designated for assignment and struggling to break into the Majors, he did nothing short of making his presence felt.

A .300 AVG, 17 homers and a decent BB/K ratio playing in the premium SS role, incredibly bad defensively as per DRS, sent him to the All Star Game in his first season, a preview of greatness to come…if only it’d all be true!

The plate discipline he showed eroded, his power production went downhill all to a 2017 season far away from his first impression: a sub .300 OBP and less than .400 SLG plus a Paul DeJong knocking the door signaled his way out of St.Louis, destination Toronto.

In Canada he found his stroke back to a 18 homers, low OBP season and that was enough for the Astros to sign him as the replacement of fan favourite swiss army knife Marwin Gonzalez, he of a flukey bang-aided, as his mediocre stints with Twins and Red Sox are proving, 2017 WS winning season.

In his last two, rather one and a half, seasons Aledmys has been as advertised: a solid bat, some pop and a lot of contact, not many Ks or walks, all while playing competently everywhere in the infield apart from shortstop, look at his 2016 defensive stats if you want to know why, and moonlighting in left field.

So why are we here? Well, because Diaz is actually being much better as of late:

Aledmys Diaz, 2021 percentile rankings

Let’s be creative and start with his defense: you may not believe it but Diaz, once one of the worst defensive shortstops to ever grace the diamond due to a strong arm but putrid range and instincts, is now a good defender both at second and third base!

Aledmys Diaz, 2021 defensive prowess

Note how he’s added success rates everywhere apart from SS, where he’s almost -1 OAA having barely played a game there, also showing his ability at handling the outfield, something that may come rather useful in what I’ll propose later on. No short but the flexibility that made MarGo a weapon for the resurgent mid 2010s Astros seem to be there for Diaz too. What about the bat? How is he doing?

Aledmys Diaz, 2021 statline per pitch type

As of now Diaz is crushing both Breaking and Offspeed stuff to a .400+ wOBA, a novelty for a fastball hitter such as Aledmys. He’s in fact expected to be much better on Fastballs than he’s being now but all things considered there seems to be no pitch type he’s struggling with…how so? Has he changed anything contact-wise?

Aledmys Diaz, 2021 contact profile

Nothing really stands out: he’s grounding balls at his usual high rate and pulling or going up the middle in 90% of his balls in play, all traits he showed since his debut, both just a little more exasperated. Note one thing though: he’s not getting shifted much (3% of his ABs) which doesn’t make sense as he’s a dead pull/middle guy, so positioning could also explain his success in part.

What’s interesting is related to his swing: Diaz has one of the flattest bath paths in the league, an old school katana slash if compared to the new Launch Angle oriented approaches, and this season he’s swinging his blade like in Kill Bill. With the lowest avgLA of his career (9 degrees) he’s hitting a ton of flares and burners, over 30%, also getting on top of 40% of the batted balls, sending them down to the ground. But that means he’s not getting under, a -10% cut with respect to 2020, and that’s for the better.

Wait, he’s also barreling at a career rate…does it make sense? Yes, and to my utmost disbelief it’s not about plate discipline:

Aledmys Diaz, 2021 swing-take profile

Ah, the good old Aledmys: a lot of swings in the zone, some chases out of it but not on Waste pitches. Every swing-related stat, from his contact and swing percentages to chase rates, is on his career norm so he’s not deviating from his swing-happy ways.

As I’ve spoilered, it’s about quality of contact and how pitchers are going after him. First of all, breakers and offspeed stuff:

Aledmys Diaz, 2021 Breaking and Offspeed heatmap

That’s a lot of pitches in the zone and your usual sliders low and away. How is he faring against them?

Aledmys Diaz, 2021 Breaking and Offspeed wOBA per zone

Strangely enough he’s getting far less from middle-middle offerings while pummeling the classic weak zone for a RHB to a .853 wOBA. That speaks to a much better approach in identifying where pitchers want to go against him and adjusting as a consequence, getting down his notoriously fast bat to square those pesky breaking balls.

Fastballs? Yep, right where you think…down the middle?!

Aledmys Diaz, 2021 Fastballs heatmap

For some reason pitchers think his bat slowed down as they are firing the gas past him without nibbling too much, avoiding the upper part of the strike zone protocol that is so trendy in 2020s baseball. And maybe they have a point!

Aledmys Diaz, 2021 Fastballs avgLA per zone

Here is Diaz’s katana slash on display: whereas many other hitters are all about getting loft, he’s squaring heaters up and in, middle and away and sending liners here and there. The only zone where he’s getting some air under the ball is the upper one: is not that Diaz can’t hit the gas, he really can, but he’s more prone to sending it in the air if challenged up while grounding or lining balls thrown down the pipe. When in doubt, a groundball is never wrong!

What does it all amount to? Diaz is doing something an economist would love: being extremely efficient with his batted balls

Here we have all of his 2021 batted balls grouped by LA and colored for EV: Diaz is smashing hard grounders, bad, but sending missiles at 10° LA, very good, while clobbering when hitting at 25° LA, you called it, Barrels!

That he’s HardHitting almost half of the time yet barreling only 8% of the time speaks to his swing, still that’s not bad for a guy who’s supposed to be a fill-in-the-gaps rather than a heavy contributor for the Houston cause.

That’s why I think he should be.

The Astros came into 2021 with a well known truth: they lost George Springer to FA and didn’t replace him in center, betting on Myles Straw to be apt to a classic leadoff role, one about bunting for base hits, hitting infield singles and stealing bags.

So far, no good: Straw is barely over .200, with no power to be spoken of, stealing some, and winning a game on his dash, bunts are nowhere to be seen and he’s getting constantly beaten or jammed harmlessly by 95+ mph heaters. He’s not chasing anything nor whiffing, both at 94th percentile or better, but he’s not walking enough nor impacting the game in other ways to make a sub .600 OPS sustainable. Oh, his defense is also on the negative as of OAA, with his burst of speed, 92nd percentile, not compensating for bad reactions and abysmal jumps.

He’s now batting eight and playing a barely average CF, all while Diaz and his above average bat wait on the bench…is there any way to change this? If I were to risk something for the sake of it, I’d try a gamble: shift Kyle Tucker from right to center and install Diaz in RF.

Yes, Tucker could probably be worse than Straw in CF as he lacks speed, but has better routes, and Diaz never played RF but I think he has all he needs to be as good as in LF: he’s got the arm and he doesn’t need to cover a lot of ground in the small confines at Minute Maid Park.

On the other hand he would vastly improve the offensive side of things: hiding in the bushes of the 8th hole, ready to ambush after the Astros’s 1–7 barrage of great hitters, Diaz could feast on starters trying to get a breather.

Is it worth the risk though? It depends on the pitcher who’s in for the Stros: if a Framber, McCullers or Emanuel, notorious groundballers, is in then I’d be much more keen to try the Diaz experiment, whereas with a Javier or Greinke, flyball inducers, it makes sense to keep the Straw alignment.

That said there’s no way to be sure about it: Diaz could very well be an atrocious RF or Straw could decide to start bunting and walk his way into a respectable xwOBA, we can’t know.

What I’m sure about is that Aledmys Diaz is a damn good ballplayer, and he deserves more ABs. Where and when? That’s up to Dusty!

Stats are updated to May 14th. Graphs, percentile rankings, heatmaps and others are all thanks to Baseball Savant.



Alessandro Zilio

Italian baseball stathead. I’ll write about MLB, NPB and Korean dramas. A lot of Astros related content and obscure references.