At this point we’re all familiar with Mazara’s struggles and the data beneath the surface of his stat-line, after all I’ve written about it before. The known quantities have been talked about to death. He continues to struggle with his O-swing rates, so far posting an O-swing right along his career averages. His ground ball rate has dropped and overall his batted ball data looks better than in 2018, but not to the extent many had hoped with the new coaching staff. Through the small sample, Mazara is currently under-performing his batted ball metrics as xwOBA suggests he should be an above average MLB hitter, but the slow start is still intriguing.

Looking at the stagnation it warrants the question of why a hitter might stagnate for multiple seasons. Often-times the answer is pitch recognition, specifically when it comes to off-speed/breaking stuff and plenty of hitters take long times to overcome this hurdle, if they ever do. The data suggests that’s not Mazara’s problem though as he’s posted above MLB average wOBAs and xwOBAs on breaking and off-speed over the past two full seasons. Looking through this data is where the first hint of a bigger problem appears, Mazara posts slightly below average offensive production against fastballs. As an additional anecdote, I’ve watched two MLB games this year close up and both times Mazara took multiple inside-out swings against fastballs he was extremely late on.

Slightly below average shouldn’t necessarily facilitate too much concern on its own but let’s take a closer look. I’ve taken a sample of hitters who are in the range of outcomes that many expected Mazara to fall within and Bryce Harper because he represents a top of the line reference for batted ball data.

Here is Mazara against fastballs in relation to these hitters since the start of 2017. (all data pulled from Baseballsavant.com):

Bottom of the list is not a great place to be, but it could be that the names I semi-randomly cherry-picked gave me an incomplete data-set to work with, so ran the same report with all hitters with over 150 PAs ending against fastballs from 2017 and found that Mazara ranks 257th out of 440 in xwOBA.

While being in the lower half of fastball hitters in the MLB isn’t a death sentence, it does limit both upside and the lower limit of ability that needs to be there to be an above average hitter. The best hitter I could find below Mazara in that data-set was either Brett Gardener or Yuli Gurriel. There are however, a plethora of prospects that we all scratched our head about: Jonathan Schoop, Addison Russell, Maikel Franco, Greg Bird, Derek Fisher, Byron Buxton, Rafael Devers, etc. There are also plenty of older hitters who have seen their post-prime careers fall off a map: Carlos Gonzalez, Chris Davis, Carlos Beltran, Ian Kinsler, etc. The lowest xwOBA against fastballs that I could find where the hitter still maintained elite production (130+ wRC+) was Javier Baez who posted a 131 wRC+ in 2018 while having an xwOBA against fastballs of .367 since 2017. While you can manipulate the data around to make it look less dire, the inevitable conclusion is that struggling against fastballs correlates strongly with lower offensive production and limits the upper end outcomes of players significantly.

That leads to another question in how much does velocity have to do with this? As the MLB continues its rapid ascension into higher average fastball velocities, it seems prudent to check into Mazara’s struggles against that trend. Here is Mazara against fastballs 92 MPH and under alongside 93 MPH and up with the same reference group:

While Mazara consistently showed up on the bottom of this list of hitters, the gap between Mazara and the worst of this grouping increased when looking at velocities 93 MPH and up.

There is one more piece we need to address before we draw any conclusions. Does Mazara have a poor xwOBA against fastballs because he’s overall a below average hitter by xwOBA or is he a below average hitter at least in part because he is poor against fastballs? His 2017-2019 xwOBA sits at .331 and league average is .320. His xwOBA against breaking balls is .310, well above the league average of .272. His xwOBA against fastballs of .345 is below the league average of .353. While not perfect, this data suggests that Mazara provides a significant portion of his value by being “less bad” against breaking pitches in order to make up for the below average returns he produces against fastballs.

As to the underlying reason for these struggles for Mazara, I can’t say yet. It could be that it’s something innate physically like reaction time or vision. It’s also possible that Mazara is regularly sitting on breaking balls, which means he must divert to an inside-out swing when he gets fastballs unless he’s specifically sitting fastball. Regardless of the reason, Mazara’s ability to do damage against fastballs compared to league average is fairly concerning for a player who should be dealing a large portion of his damage on the easiest for MLB hitters mash on the average. It’s possible that Mazara can create enough value against breaking/offspeed offerings to negate the gap in value he doesn’t provide on fastballs, but it seems to me like this would be a point of focus in his development if it is something that can be mended.