Young & Old Hitters Need a Nap

While digging through Mining the News, I found this quote on José Abreu.

All three of Abreu’s hits, including his solo home run on Saturday, arrived in games that immediately followed an off day. During Abreu’s resurgence last October, team officials and coaches cited the plethora of postseason off days as one factor for Abreu’s increased production.

The question opened a Pandora’s box of possible studies but I kept to a simple quick approach to see if extra rest helps a hitter. The findings supported common sense but more should be done.

During the 2023 regular season, Abreu posted a .211 AVG in the second of back-to-back games and a .298 AVG when he got a break. Also, his Basic wOBA (*) was .272 without a break and .359 with one. The struggles have continued this season with a .072 wOBA on back-to-backs and .261 wOBA when he has a break. The team is taking action based on the information so we should also.

For my dataset, I looked at all hitters with at least 50 PA in a season and compared their results when they played back-to-back games and when they didn’t. I only look at 2021 to 2023. So many rule changes happened after 2020, that I wanted to reset the league norms.

First, here are the hitters plotted with the difference and their age.

As I thought, the results are a mess. Here is a different approach that places the info into four age groups.

It’s not a huge surprise but hitters play better with rest (.0044 wOBA improvement or ~3% better). I’ll ignore the batting average values since they are too close together.

Generally, the overall wOBA differences make sense with the young players getting used to the grind, regulars thriving off the grind (possible survivor bias), and older players being … well … old.

As for what can be done for fantasy purposes? Not a whole lot but don’t be surprised if older hitters struggle to maintain their stats and need breaks. While I’m not against rostering older players, fantasy managers must know the risks associated with them.

As for more research, finding the year-to-year stickiness of the difference should be the first step. If it is sticky, struggling hitters will continue struggling and won’t be able to bounce back. If the rate isn’t sticky, there isn’t much to add to projections. Besides the stickiness, the years can be expanded to see if the difference changed over time. Another option would be to see one trait cause the difference like power or strikeout rate.  Finally, the difference could be compared when playing three, four, or more days in a row.

With the season going on, I don’t have the time to investigate every possible avenue. If someone else doesn’t dive into the subject between now and then (someone in DFS should or already has), I might relook this off-season.

Most of my studies find jack squat, but this one explains why some young and older hitters might struggle. The production drop could be seen by more bench time or decreased production.

* Basic wOBA = (.7* (BB + HBP) + .9*1B + 1.25*2B + 1.6*3B + 2*HR)/PA