Before any other information is presented, I wanted to compare these two players totally anonymously. This snapshot of statistics provide some insight into batted ball data, plate discipline and physical abilities. There is much more to this story but this provides a baseline of comparison for two players perceived as being vastly different.
Which player would you rather have? Judging by just the provided information, Player X has a slight edge with better contact skills whereas Player Y has slightly more intriguing physical capabilities. Given this information, preference for either player is marginal considering how close these stats are. Well, one of these players is an MVP and the other may get his first chance as a starter this coming season.
Player Y is Christian Yelich and Player X is Yandy Diaz. The point of this article, however, is not just to show where they are similar, but how they are different and what varies between these players that is not represented in this snapshot of statistics. Perhaps, by learning what Yelich does we can see what Diaz must improve to reach that level. What is important about many of these factors is that they are difficult skills to just acquire with adjustments. Hitting the ball hard, making contact, and having plate discipline are not characteristics that can be explained by luck and Yelich has managed to be successful with similar attributes to Yandy.
On ground balls this past year, Diaz had .262 xwOBA on groundballs while Yelich had a .240 with Diaz owning a 3 MPH Exit Velocity advantage. On line drives, Yelich’s .730 xwOBA bested Diaz’s .679 but similar launch angle and exit velocity numbers suggest it was probably an insignificant true difference. On fly balls, however, Diaz’ xwOBA .362 pales in comparison to Yelich’s .953 xwOBA. The major difference in these two players is their production on fly balls. Diaz has an 88.2 MPH average velocity on flyballs whereas Yelich has a 99.4 MPH average. As far as physical skillset, we see similar abilities with the close proximity of Exit Velocity and Sprint speed, while also possessing well above average plate discipline. Diaz’ plate discipline may be better all in all considering the smaller K%-BB%. So why is there such a significant gap in production on fly balls?
A fairly simple, rough estimate of attack angle can be derived from a player’s batted ball profile. Attack angle is the angle in which the bat is traveling at the point of contact. We can assume that most of a player’s hardest hit balls are hit where the launch angle of the ball matches the attack angle of the bat. This makes sense logically as the more square on the ball is hit, the harder it will come off the bat. Think if you are playing tennis, can you hit the ball harder when trying to slice down and create backspin or when you serve and hit the ball straight on. With that, I wanted to take a look at the batted ball events for both Yandy and Yelich and see if I could find any differences.
Here is Diaz’s data:
There is not a huge sample size for Diaz but there are 90 batted ball events that we can learn from. Looking across the x axis, the hardest hit balls seem to culminate under 10 degree launch angle. Looking at his 10% of hardest hit balls, the average launch angle is 3.6 degrees. Again, this is a very rough estimate but it does make sense that Diaz is well below league average for attack angle at about 4 degrees. He is just barely swinging up on the ball in a league that continues to try to hit the ball in the air more and more. Now to compare with Yelich:
There is clearly a much larger sample size, but it does look like those hardest hit balls come together at a higher launch angle than Yandy. In fact, on Yelich’s top 10% of hardest hit balls, his launch angle averaged 13.3 degrees. This has been a trend for Yelich as his average launch angle has slowly increased since 2015 when the data was first tracked. Obviously enough, a higher attack angle usually leads to a higher average launch angle and 14 is probably right around league average. Why is this important? Well, all things equal, a batted ball with 1000 RPM of Backspin hit at Yandy’s max EV of 99 and 30 Degree Launch Angle travels 395 feet. If we increase that EV to Yelich’s 113 max on flyballs and lower the spin to about 300 RPM that same fly ball travels 440 feet (per Dr. Alan Nathan’s Batted Ball Trajectory Calculator).
With a difference of about 10 degrees on their hacks, Yelich simply has a higher angled swing than Diaz which explains the difference in production on fly balls. This is not really a surprise, especially when taking a look at the difference in Exit Velocity in Diaz’s Fly Balls/Linedrives compared to groundballs. Diaz’s 1.9 MPH difference is the 15th lowest in the MLB (min: 90 BBE) which constitutes the 3rd percentile. Yelich on the other hand has an 8.2 MPH difference, good for the 60th percentile in the league. There does not necessarily need to be an enormous difference in order to be effective but Yelich is definitely trending in the right direction whereas Diaz is at the level where a change is needed. Diaz ranks 22nd in the league in average exit velocity, just behind the 20th ranked Yelich and the 21st ranked Mookie Betts. Of those 22 players, Diaz has the 4th best BB/K ratio behind Betts, Miguel Cabrera, and Robinson Cano. This is backed by the fact that Diaz swings at 70.3% of pitches in the zone and only 21.4% of pitches out of the zone, which was the 3rd largest difference in this grouping of 22 players.
If you are reading this and feel like I am cherry picking stats than you are absolutely right. As of right now, Yandy is not a productive player. However, the point of this article was to show that Diaz has the tools to become an effective player. He has the batted ball ability and plate discipline that rivals the best hitters in the league, and a few mechanical adjustments could get him there. Looking forward, I am worried about how the Rays utilize Diaz. Hitting Coach Chad Mottola and the rest of the Ray’s staff have taken a more contact and ball in play-centric offensive philosophy, in lieu of a power based approach. The optimist in me sees that Diaz is a perfect fit for such an approach and could be very successful. However, the pessimist in me says Diaz will continue to not tap in to his possible elite power. The Rays are usually at the forefront of being able to successfully utilize their players and we saw Tommy Pham go to Tampa Bay, increase his average launch angle and tear up Tropicana. I am looking forward to Diaz’s season with cautious optimism and hope we see his potential start to pan out.
Data Courtesy of Baseball Savant and Fangraphs
Feature Image Courtesy of Wikimedia Commons