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Just How Good WAS Yainer Diaz? Did Dusty Baker Deprive him of Rookie of the Year?

If his manager had no faith in him, why should the ROY voters?

MLB: ALCS-Houston Astros at Texas Rangers Andrew Dieb-USA TODAY Sports

Earlier this week, I published an article arguing that rookie Yainer Diaz showed remarkable adaptability during the course of his 377 plate appearances this year. His obvious Achilles heel was his tendency to swing wildly outside the strike zone, although somehow this did not translate into a high K%. He did show improved plate discipline as the season progressed.

It seems I put the cart before the horse. I did not anticipate that I would need to argue that he was an excellent, even elite hitter, despite his one major flaw. That seemed obvious. And yet many people seem to be fixated on the embarrassingly bad pitches Diaz sometimes swung at, rather than his 23 home runs, some of them on the aforementioned bad pitches.

So, in the spirit of this post-Thanksgiving season, I thought it would be helpful to compare Diaz’s performance on a per plate-appearance basis to some of MLB’s elite home run hitters. And to show that even though Diaz swung at too many bad pitches, he actually struck out less than average compared to other elite power hitters.

Later, I want to argue that, if given the playing time he deserved but did not receive, Diaz would have had a strong case for rookie of the year.

Here is a chart of baseball’s top 11 home run hitters.

And here is Diaz.

Diaz hit a home run every 16.3 plate appearances. That made him more prolific than three of these sluggers, and a rounding error from Adolis Garcia, who makes an excellent comp. (Almost identical wRC+ and ISO as well) Diaz’s wRC+ is equal to or better than four members of this group and one point from another. Translated out to 600 PAs, at his current rate Diaz would have hit 37 home runs, tied for tenth in MLB.

And rather than being some sort of strikeout king, his K% is among the lowest in this list of home run kings. Only Ronald Acuna and Mookie Betts had lower K%s.

Although opinions differ as to the relevance of the following stat, hitting as a catcher Diaz was much better, earning a 170 wRC+, with 14 homers in 187 PAs, or one homer for every 13.4 PAs. That would be third best among these top sluggers. His wRC+ as a pure catcher would have trailed only Shohei Ohtani and Aaron Judge.

His K% was only 13.4%, below the Mookie line! This last stat supports my opinion that playing behind the plate improved Diaz’s concentration and focus as a hitter. It was true of Evan Gattis as well.

There were other notable, possible future Hall of Famers who, like Diaz, did not get enough PAs to compete for the home run title. Let's compare some of these familiar names to Diaz.

Other Notables

In terms of PAs/HR Diaz was within a rounding error of Corey Seager and....yes....our favorite, Yordan Alvarez. For this season, Diaz left Mike Trout and Bryce Harper eating his dust. And he had a lower BABIP by far than all of them. (And not because he’s a slow runner. Statcast has him faster than over 50% of MLB baserunners)

Now, let’s compare Diaz to the three position players that received more ROY votes.

This chart shows that there’s not a big difference between Henderson, Casas, and Diaz overall as hitters. Henderson played a key position, shortstop, and had plus defensive stats. But Diaz showed some good chops as a defensive catcher, and if he had won the home run derby between these three with the projected 37, as well as accumulated other counting stats, could he have gotten the nod?

We’ll never know. Not thanking you, Dusty.

And once again, for those who think the rookie Diaz was a strikeout king, compare his K% to his ROY competitors or rookie Alex Bregman, today’s gold standard for plate discipline. Bregman K’d 24% of his PAs as a rookie.

One last objection. Some say Diaz never had a meaningful hit. Good or bad clutch hitting within a single season is widely regarded as a small sample size anomaly. But just off the top of my head, I can think of three games the Astros won because of key hits by Diaz. Keep in mind that they tied for the division lead.

Against Colorado, Diaz hit two home runs in Denver in a 6-4 win. And at home against Baltimore in September, as a late-inning replacement for Martin Maldonado in a tied game, he led off the ninth inning with a double. He scored the walk-off run after a Mauricio Dubon single. His scoring that run was the photo I used for my article earlier this week. And, as commemorated in the picture above, Diaz was on base when Jose Altuve hit his game-winning home run in Game Five of the ALCS.

No one can say for certain whether Yainer Diaz will improve or not this season. But let’s at least acknowledge how good he was this year despite unnaturally attenuated playing time. Who knows, with daily reps, playing catcher, and his adaptability, he might stand a good chance of improving.

And if swinging wildly at times as a rookie means you have no future, then Jose Altuve and Yuli Gurriel must have turned out to be really bad baseball players.