At the MLB owners meetings earlier this week, the competition committee agreed on a motion to raise the bottom of the strike zone from the hollow below the knee cap to the top of the hitter’s knees. That change isn’t a done deal for 2017—or at all—but it is an interesting idea for an attempt to cut down increasing strikeout totals in baseball. The ESPN Stats and Info tweet in that previous link shows the marked increase of called strikes in the lower third of the zone in recent seasons, a trend no doubt influenced by teams’ recent dedication to pitch-framing catchers.
Mike Petriello of MLB.com wrote about this topic on Tuesday and identified the pitchers from 2016 who threw the highest percentage of their pitches in the bottom ribbon of the strike zone that the committee proposed could become balls. He also listed the pitchers who saw the most called strikes in that part of the zone, which directly addresses the motivation to reduce strikeouts. The pitchers on those lists would undoubtedly be among those most affected by a change in the bottom of the strike zone, but I also wondered whether there could be more to it than that. Pitchers pitch to the bottom of the zone not just to earn taken strikes but also because those pitches are more difficult to hit than those in the heart of the zone, and so I wanted to research overall pitcher performance in the bottom ribbon.
Piggybacking on Petriello’s and Jon Roegele’s research that identified the proposed zone change as between about 18 and 21 inches off the ground, I divided the entire strike zone height vertically into 10 zones of about 3 inches per zone (balls inside and outside off the plate are included but balls above and below the zone are excluded). Then, I calculated not only the taken strikeout rate but also the swinging strike rate and BABIP of all hitters in those zones.
|Zone||Approx Inches Above Ground||Taken K%||Swinging K%||K%||BABIP|
|10||45.0 – 47.9 inches||3.8%||22.6%||26.4%||.245|
|9||42.0 – 44.9 inches||5.7%||19.7%||25.4%||.268|
|8||39.0 – 41.9 inches||6.1%||14.5%||20.6%||.268|
|7||36.0 – 38.9 inches||5.5%||10.3%||15.8%||.287|
|6||33.0 – 35.9 inches||4.7%||9.0%||13.7%||.298|
|5||30.0 – 32.9 inches||4.6%||7.3%||11.9%||.307|
|4||27.0 – 29.9 inches||5.1%||7.3%||12.4%||.312|
|3||24.0 – 26.9 inches||5.8%||8.0%||13.7%||.326|
|2||21.0 – 23.9 inches||7.4%||10.0%||17.4%||.319|
|1||18.0 – 20.9 inches||7.3%||14.2%||21.5%||.295|
Interestingly, the bottom ribbon of the zone has an almost identical taken strikeout rate as the zone just above it, which would become the new bottom of the zone if the proposed change takes effect. That rate of about 7.3 or 7.4 percent is much higher than the zones above it, so even though there might not be any difference in taken strikeout rate in the very bottom of the current zone or the proposed new zone, cutting the height of the taken strikeout “red zone” in half would definitely hurt pitchers.
But beyond those taken strikeouts, look how dramatically swinging strikeout rates increase in the bottom ribbon of the zone. Compared to the proposed new bottom of the strike zone, hitters strike out an extra 4.2 percent in the current bottom ribbon. And BABIP is 24 points lower in the current bottom zone than the one just above it. Those trends show that hitters not only take more called strikes at the bottom of the zone, they struggle to make solid or any sort of contact in the bottom ribbon.
Both the strikeout and contact quality concerns can be more neatly summarized with wOBA, which, not surprisingly, is lowest in the bottom ribbon of the current zone.
|Zone||Approx Inches Above Ground||wOBA||Diff from Zone Just Above|
|10||45.0 – 47.9 inches||.295|
|9||42.0 – 44.9 inches||.296||-.001|
|8||39.0 – 41.9 inches||.301||-.005|
|7||36.0 – 38.9 inches||.333||-.032|
|6||33.0 – 35.9 inches||.346||-.013|
|5||30.0 – 32.9 inches||.371||-.025|
|4||27.0 – 29.9 inches||.362||.009|
|3||24.0 – 26.9 inches||.363||-.001|
|2||21.0 – 23.9 inches||.332||.031|
|1||18.0 – 20.9 inches||.289||.043|
These results may seem like common sense, but I think they provide an important foundation of understanding which pitchers would be hurt the most by a raised strike zone. Overall, pitchers in 2016 allowed a .289 wOBA on their pitches in the bottom ribbon of the strike zone and a .344 wOBA on their pitches in the rest of the vertical zone. The difference between those is 55 points. Looking at the pitchers with at least 175 plate appearances that ended with a pitch in the bottom ribbon of the zone since 2014, the most extreme beneficiary of that bottom ribbon saw nearly three times that average difference.
|Pitcher||Zone 1 wOBA||Other Zones wOBA||Diff|
|Jorge de la Rosa||.244||.361||.117|
Yep, it’s Stephen Strasburg. He wasn’t one of the pitchers Petriello identified as throwing the most pitches or drawing the most taken strikes in the bottom ribbon, so perhaps it is just a case of hitters being unable to handle his stuff when he locates to the edges of the zone. Still, this list and Petriello’s list of taken strike leaders are not totally dissimilar. Martin Perez and Jake Arrieta are in each top 10, and a lot of Petriello’s leaders didn’t make the cut in my list based on the 3-year cutoffs I used for sample size reasons.
I suspect that pitch repertoires are an important part of this equation. In particular, note that Masahiro Tanaka and Hisashi Iwakuma both made my top 20 and represent two of the only three qualified starters who have thrown split-finger fastballs more than 10 percent of their pitches since 2014. Michael Pineda is also the heaviest slider-user in that period, and he landed eighth on the list.
With the cutoffs I used, 69 starters qualified. Of those, only three allowed worse wOBAs in that bottom ribbon than in the rest of the vertical zone: Ervin Santana (3 point difference), Justin Verlander (12 point difference), and Chris Tillman (40 point difference). I’m impressed. With these results, I suspect a change in the bottom of the strike zone would not only dramatically decrease strikeouts, it could spark an offensive resurgence even greater than the speculated juiced balls phenomenon over the past 18 months.
Scott Spratt is a fantasy sports writer for FanGraphs and Pro Football Focus. He is a Sloan Sports Conference Research Paper Competition and FSWA award winner. Feel free to ask him questions on Twitter – @Scott_Spratt