Diamondback Batters Will Improve

Like David Peralta, young D-backs’ swings will likely improve for several years. 

Let’s start from a simple idea. When baseball players, specifically batters, reach the Majors they make adjustments so that in general their batting results continually improve (albeit with natural slumps and hot streaks).

For each season, let’s use swing score to measure batting results. Swing score is calculated by looking at swing efficiency (balls-in-play divided by swings), hard hit percentage, homers per plate appearance, exit velocity for home runs, line drive percentage, and exit velocity for line drives. When a batter is better than league average, he is awarded points. Point values follow:

• 40 points swing efficiency
• 15 points hard hit percentage
• 15 points homers per plate appearance
• 5 points exit velocity for home runs
• 15 points line drive percentage
• 10 points exit velocity for line drives

As of 5 July, Christian Walker and Ketel Marte had the highest swing scores (80 out of 100). For more detail about swing scores see this AZ Snake Pit article.

The Diamondbacks farm system has high-ceiling batters who will soon graduate to the Majors. This year four position player prospects made their debut with the Diamondbacks. In the next couple years, more prospects are expected to join the team.

This season, many Diamondbacks batters are young and inexperienced. Through 9 July, the following nine Diamondbacks batters have very few career plate appearances (PAs) in the Majors (please note each of these players had between zero and 86 PAs at the start of this season):

• Buddy Kennedy, 64 career PAs.
• Jake Hager, 89 career PAs.
• Drew Ellis, 100 career PAs.
• Jose Herrera, 100 career PAs.
• Seth Beer, 103 career PAs.
• Cooper Hummel, 148 career PAs.
• Jake McCarthy, 156 career PAs.
• Alek Thomas, 204 career PAs.
• Geraldo Perdomo, 300 career PAs.

Let’s look at whether Diamondbacks batters will improve as their plate appearances increase. What would make sense is that players improve until they reach a peak, and then they experience an age-related decline. What does that typically look like for a Diamondback batter?

Let’s look at David Peralta. So far, he played in 9 seasons. The following graph shows David Peralta’s swing scores from 2014 to 2022 and how they compare to his career plate appearances at the end of that season. The dashed line represents a least squares fit to the curve that makes sense (players improve until an age related decline). His peak swing score happened at 2239 plate appearances.

David Peralta 2014 to 2022, Data from Baseball Reference and Baseball Savant.

Let’s look at this season’s swing scores for the Diamondbacks players with at least 60 plate appearances through 5 July. Their swing scores were between 15 and 80 (100 points maximum). The following graph shows red diamonds that represent their swing scores and plate appearances. Davis Peralta’s curve is shown as a purple dashed line. Assuming that is a typical progression as plate appearances increase, eight Diamondbacks have less than 1100 plate appearances and therefore will continue to improve as they approach their peaks near 2239 plate appearances.

Diamondbacks with minimum 60 PAs through 5 July. Data from Baseball Reference and Baseball Savant.

Two batters stood out (Alek Thomas and Jake McCarthy), each with less than 200 career plate appearances and with high swing scores of 70 and 60. If they improve at the same pace as David Peralta, in a few seasons they will reach All-Star level peaks.

Buddy Kennedy was not shown on the graph due to only 53 plate appearances this season. His provisional swing score was 85 (outstanding), showing he has potential to reach an All-Star peak.

Batters with at least 60 plate appearances this season, and with less than 1100 career plate appearances, and therefore have improvement potential follow: Jose Herrera, Seth Beer, Cooper Hummel, Geraldo Perdomo, Daulton Varsho, Pavin Smith, Jordan Luplow, Josh Rojas, and Carson Kelly.

Homers per Plate Appearance.

One component of the swing score was homers per plate appearance. This season in the Majors, averages for three age groups shows that older players hit less homers. The following graph compares the Diamondbacks (averages in each age group and a few players that exceeded the averages). A surprising conclusion is that the Diamondbacks have an opposite trend: older players hit more homers. A caveat is that one team for one half a season is a small sample size. Specific players on the Diamondbacks made a big impact, such as Luplow and Walker.

Data from Baseball Reference.

Summary.

David Peralta’s career shows a typical batter whose swing gets better until about 2200 plate appearances, and then it slowly declines. This season, we saw a dozen Diamondbacks batters with less than 1100 career plate appearances. Nine batters had 86 or less career plate appearances at the start of this season. Like David Peralta, their swings will likely improve for several years.

This season for the league, on average older players hit less homers. The Diamondbacks had an opposite trend: older players hit more homers. Specific older players like Christian Walker made a positive impact.