RADIO
David Emerick analyzes Tampa Bay Rays third baseman Yandy Diaz's breakout season and whether he can continue his recent power surge against expectations from skeptical fantasy baseball managers.
When the Tampa Bay Rays traded Jake Bauers and cash money to acquire Yandy Diaz, it was a move that seemed to prompt both excitement and head scratching. Bauers was already an everyday outfielder who projected as an above average outfielder very soon. Diaz was a toolsy but frustrating player chiseled of the same stuff as the statues of Greek gods.
The argument for both sides was obvious: the Indians needed a cheap but effective outfielder to add to their lineup. The Rays thought they could rectify whatever kryptonite was plaguing Diaz.
For many, the move seemed far riskier for Tampa Bay, which was sending away the younger and more accomplished player in hopes of cashing in on Diaz's upside. A month into the season, it looks like the Rays made the right move.
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Let the Good Times Roll
During his 88 games with Cleveland, Diaz had one home run. As I write this, Tampa Bay is 30 games into the season, and Yandy Diaz has hit seven home runs. I know that in this day and age of complex sabermetrics, all of the data can be complex, so let me break this one down a little bit.
Important Maths
7/30 > 1/88
The home run total might be a rough metric here, but it’s a good representation of how different the results have been. Fantasy owners might have drafted Diaz at around pick 250, but he’s been performing like a top-100 player with noticeable improvements across the board.
| ISO | OPS | wOBA | wRC+ | |
| Cleveland Diaz | 0.110 | 0.797 | 0.346 | 115 |
| Tampa Diaz | 0.275 | 0.918 | 0.382 | 144 |
The sole exception has been batting average, which is down from an inflated .312 last year and closer to league average at .264 this season. So what has changed and how sustainable is it?
Please Prepare Your Body for Launch Angle
If we look more closely, there are definite changes in Diaz’s approach this season. Over the last few weeks, Diaz’s launch angle of 5.2° has crept up above his 4.4° from 2018, and his exit velocity on line drives and fly balls is much better. Last year, his exit velocity on balls in the air was 93.6 MPH, closest to Jonathan Villar. This year, it’s 97.6, right between Cody Bellinger and Nelson Cruz.
The 5.2° launch angle means that we aren’t dealing with an exaggerated uppercut swing or extreme flyball tendency. Diaz’s swing remains fairly level, but it’s producing better results. Diaz has dropped his groundball-to-flyball ratio from 2.29 last season to 1.67 this season. Add the extra velocity to those additional fly balls, and you get the additional power that Diaz has showcased.
Let’s take a look at Diaz’s swing from last season and this season:
First a 2018 inside four-seamer
Now a 2019 inside four-seamer
The 2018 swing produces a groundout to the shortstop. The 2019 swing produces a 428-foot home run.
Both pitches are middle-inside four-seam fastballs around 92 MPH, but Diaz’s head moves less this season, his swing is more synced up, and the bat comes through the zone closer to the plane of the ball in comparison to 2018, which looks almost perfectly level. That adjustment would help to explain why Diaz is getting to his game power more effectively. Last season, Diaz was barely ever able to take advantage of pitches thrown down the heart of the plate. This year, his swing is better suited to punish those pitches.
It’s not clear that Diaz is now 30-home-run player, but he looks like a good bet for 25 home runs and a .275 batting average.
Here is Diaz’s 2018 slugging chart courtesy of FanGraphs:
Here is his 2019 slugging chart:
Like the table above, the results between the two seasons are vastly different. Looking more closely at 2018's results and his swings, I’d hypothesize that the success on pitches up in the zone and pitches down in the zone (while struggling with pitches in the middle of the zone) comes from Diaz using two very different swings.
On most pitches in 2018, Diaz used that nearly level swing, which meant lots of groundouts on middle-middle pitches that he should have been driving. When the ball was low, however, Diaz would sometimes drop his bat down and use a swing closer to the one in the 2019 clip. The problem for him was that he wasn’t using that swing for other pitches.
We can see in the 2019 chart that Diaz is still thriving against pitches above the waist, but he’s applying his power better in the heart of the zone. Pitchers are beating him inside, but Diaz's plate coverage is dramatically improved. Both sample sizes are smaller than ideal (469 pitches for 2018 and 483 for 2019), but the data here matches the results so far.
Let’s Grow Together
The Rays obviously invested in Diaz with the intent of modifying his approach at the plate and the hope that he could provide power and on-base skills to a team looking to compete this year. Even without the apparent swing change, Diaz has improved his approach at the plate. Or he’s finally been able to return to the approach he used in the minors.
Diaz’s walk rate in his first two seasons was 10.7%, and his strikeout rate was 18.1%. This season, he’s sitting at a 13.5 BB% and a 16.7 K%. Diaz is swinging and missing more frequently, but he’s reaching base almost as often while generating far more power.
The combination means that while Diaz’s batting average is taking a hit this season, he should maintain just as many run and RBI opportunities, especially in the Rays’ sneaky good offense.
Just Hold Me and Watch the Fireworks
It’s worth noting that Diaz has looked a bit erratic at times. He’s consistently produced all season, but he also looks like a younger player still making adjustments even though he’s 27. However, it’s hard to watch Diaz, look at the potential and not feel convinced that the performance this season is legitimate. Managers who own Diaz are encouraged to hold onto him as a player whose performance will likely exceed his trade value. Conversely, if the owner in your league is looking to cash out, there's little reason to worry that the performance has been a simple hot streak.
That said, let’s just take a minute to watch the fireworks.
