Why We Missed: Yelich & Peralta

The offseason always gets my mind wandering and looking for coincidences that eventually lead to projection adjustments. In my contemplations, I stumbled on Christian Yelich and David Peralta exceeding expectations while posting groundball rates over 50%. To maintain this high groundball rate, they must use a fairly flat swing. This information by itself is completely useless but when combined with the latest pitching trend of high fastballs, I thought I may have something. I decided to mash these two ideas together to see if groundball (i.e. level swing) hitters are beating their projections as the league throws more high fastballs. For those wanting the condensed version, they don’t. For those who like numbers, continue.

Pounding the top of the strike zone helps to limit the damage done by hitters with positive launch angle swings. A high straight pitch means the bat’s barrel has limited time in the area of solid contact. Pitchers have figured out the greatness of the high fastball and have been throwing it more.

Percentage of four-seamers in the top half of the zone.
2015: 52.1%
2016: 52.7%
2017: 55.0%
2018: 55.7%

With the jump in high fastballs from 2016 to 2017 and 2018, I compared the results from 2016 to 2017 to 2018 for hitters with at least a 50% GB% (min 50 PA each season). Sixty hitters made the cut.

Starting with power measurements, the average ISO increased .002 from 2016 to 2017 and dropped .001 from 2017 to 2018. No noticeable change. While Sporer’s twin and Peralta hit for more power, the average groundball hitter didn’t.

I moved onto OPS to find their overall value and from 2016 to 2017, their average OPS dropped .001. But then from 2017 to 2018, the average OPS dropped by .038. This change was significant and after digging in, most of the changes were BABIP related (i.e 21-point drop) with some plate discipline decline. Some of the drop may be from aging (from age 27.7 to 28.7) but not all of it.

While could start looking into subsets of subsets to find something useful, I stopped. The big question is if groundball hitters are performing better with more high fastballs and the answer is no. If anything, they perform worse. Now, I’m off to quickly punch out a Mitch Hanigar “Why We Missed” article.