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What to expect from St. Louis Cardinals rookie Aledmys Diaz

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St. Louis Cardinals rookie Aledyms Diaz hit a pinch-hit home run on Friday night. As rookies go he is a bit under the radar but he bears close watching and could be a significant contributor for the Cardinals. Let's take a look.

From the 2016 Baseball Prospect Book:

Aledmys Diaz, SS, St. Louis Cardinals
Bats: R Throws: R HT: 6-1 WT: 195 DOB: August 1, 1990

2014: Grade C+; 2015: Grade C+

A Cuban defector signed to a big league contract in March 2014, Diaz was limited by shoulder problems in his first season but was healthy for most of 2015. He was cut from the 40-man roster in July but was restored to it in November after it became apparent he would likely be selected in the Rule 5 draft following a hot second half and overall solid campaign in the high minors. When he signed, Diaz was advertised as a line drive hitter with good plate discipline, a touch of power, and steady defense. Much of that has panned out: he can be impatient but keeps his strikeout rates reasonable and showed substantial power in the second half, slugging .559 (and hitting .317) in his last 41 games. I’d rate him as solid-average as a shortstop, not excellent but certainly playable there if he hits enough. It looks like he might very well hit enough. Don’t overlook him. Grade B-.


Diaz hit .265/.316/.353 in 34 at-bats this spring, not spectacular but enough to get him a job on the bench. Sabermetric projection systems aren't enthusiastic, Steamer projecting him at .256/.298/.352, ZiPS at a nearly identical .247/.290/.383.  PECOTA at Baseball Prospectus is a bit happier with Diaz, projecting him at .257/.304/.411.

I think he's better than that; I think this is a guy who could hit .270/.310/.420, just to throw some numbers out there. This is based on seeing him late last year when he was tearing up the Pacific Coast League. During that run he demonstrated very good bat speed and a quick swing, plus substantial pull-side power. His batting eye isn't bad and he did a good job handling both breaking pitches and harder stuff.

But as noted, that's what he was doing during his late hot streak; small sample sizes can be deceptive, both on paper and in person. Earlier in the year and certainly in 2014 he was less effective.

Can he do the good stuff over the longer haul?

My opinion is that, yes, Diaz can get hot often enough to put up the .270/.310/.420 line above, or at least a better line than the sabermetric systems project. Add that with competent shortstop defense and you have a player.

I don't know if the Cardinals agree, but that's my take. Your mileage may vary.