Ok I Guess I'm Talking About Sliders

Trea Turner likes slides.

Trea Turner also likes sliders, all of a sudden.

After watching the top of the Phillies order perform acts worthy of the 2016 squad since the dawn of the second half, I've been wracking my brain, trying to piece together what is going on that has caused our June fire offense to regress so... infuriatingly. The unspoken mouthpiece of this gully has naturally been our shortstop of the next 11 years, but its hard not to ignore these performances over the past 30 games:

Kyle Schwarber:.194/.271/.403

All Star Nick Castellanos: .198/.236/.372

Brycey Boy: .306/.384/.414

JT: .222/.303./444

Put simply, it hasn't been particularly pretty.

So what's going on? Well it's hard to come upon a common theme. Harper seemingly doesn't have his power back, Trea is striking out significantly more, JT looks like a shell of his former self, Nick seems to be free swinging lately, and Schwarber is no longer in June. Troublingly, this has been an issue all season, with none of the stars being able to string together sustained months of success. I cannot claim to know the mechanics of each star, but after scraping through Fangraphs ad nauseum, I have come upon one thing that might be contributing to this inconsistency:

The slider

Now as is regularly demonstrated, being able to hit the fastball is correlated heavily with slugging and overall batting skills, but the way each of the big Phily stars has approached the slider is perhaps just as telling in how they've performed this year. Consider: The slider, as the second most widely used pitch in most pitchers' repertoires, is the key in hitters getting contact with two strikes and spoiling to wait for the fastball. If you sit slider during an at bat, you are essentially sacrificing some exit velocity and likely upward trajectory in favor of contact and protection. So how have our stars been doing against the slider?

Fangraphs Run Value (per 100 pitch) |||| Fastball Run Value (per 100 pitch)

JT Realmuto

2022 3.8 (.61) |||| 17 (1.58)

2023 2.9 (.79) |||| -4 (-.65)

Bryce Harper

2022 6.6 (2.33) |||| 9.6 (1.33)

2023 -4.3 (-1.63) |||| 7.5 (1.72)

Kyle Schwarber

2022 4.9 (.85) |||| 13.4 (.99)

2023 -1.3 (-.3) |||| -.4(-.05)

Nick Castellanos

2022 -1.9 (-.28) |||| 1.8 (.21)

2023 6.4 (1.42) |||| 7.7 (1.25)

Trea Turner

2022 -.34 (-.45) |||| 17.9 (1.49)

2023 8.9 (2.07) |||| -9.9 (-1.24)

I want to highlight a few things that each slider stat is instructive about. First: Realmuto seems to failing to adjust to how the fastball and slider play to him. Though his run expentancy is lower overall against the fastball, JT has seemingly been hunting the fastball to abandon, to the point where his BB% on fastballs is 2.3% this year compared to 9.6% the year before. You know what rate experienced the opposite trend? The slider, which he seems to be laying ignoring on close pitches and outside the strikezone (11% walks vs 7.8%). However, a lot of that walk rate has come as a result of pitchers throwing significantly more fastballs to JT in the zone, compared to sliders, which he has seen leave the zone at an alarming rate. All the while, Realmuto's swing percentages on the fastball haven't changed significantly and he's swinging at fewer sliders outside the zone. Why is this less effective? Seemingly, it has something to do with the interplay. Because more sliders are thrown outside the zone, Realmuto is getting worse and worse contact when he swings inside it, to the point where every one of his flyballs hit off the slider is a popup. It's possible that in taking the same approach on fastballs, JT's eyes are trained more towards that swing path and he's shifting it more radically when encountered with offspeed. Honestly, this one was a strange one to analyze over all. To the simpler ones!

Second: Bryce and Kyle

Now the value changes on each of the big sluggers sliders has been pronounced, but the run value changes weren't necessarily due to changes in walk or k rate. What was interesting to me is how each slugger is seeing more than a real spike in slider usage at the expense of the fastbell. Schwarber, who was never great at ignoring sliders (39.7% career K rate against. Yeesh) saw his usage bump from 19.9% in 2022 to 22.7% this year. For a man who sits dead fastball each time, pitchers choosing to up offspeed usage and using them effectively might signal his downfall. For Bryce, a growth from 17.7% to 23.5% is whopping. For a man who is struggling to elevate the ball, is it surprising that pitchers have leaned in? Harper's GB% on sliders alone has jumped nearly 13% alone from last year (his line drives have disappeared off it), so we should continue to expect this usage from here on out.

Third, a tale of two Nicks

Much of Nick Castellanos' resurgence this year can be contributed to his better pitch selection. While his slider k rate has skyrocketed and his zone contact percentage has gone down, Castellanos has done something interesting when hitting the slider. First, he's looking at more pitches out of the zone (5% subtraction in O-swing on the pitch), so he's hitting better pitches overall. Second, his LD rate has jumped the same 5% on the slider, all at the expense of the flyball. Put simply, he's swinging harder at in zone sliders. He might miss more, but he's certainly taking more for doubles and homeruns. The trouble is, his slider percentage is already lower than last years. What happens to Castellanos when pitchers start to throw him more offspeed in the zone? This past month might be the sign of things to come.

Finally Trea

Oh Trea. Treadle Treadle Treadle. This year, Turner seemed to guess wrong, or at least guess strangely. Kevin long and co must have seen Turner's approach and thought to themselves "Wow, Turner really can't hit the slider. What if we gave him the JT treatment?" Like Castellanos, Turner is swinging less at outside sliders (down 5.5%) and missing more on zone sliders (down 7%), but hitting the ones he hits for more power (hr/fb up 4%!). As a result, this has been Turner's best year against the slider in his career!. HOWEVER, whereas Castellanos stayed in his zone with Fastballs (swing percentages essentially haven't changed against the pitch), Turner has let himself get caught in slider madness as he is swinging at outside fastballs now too, presumably those above the zone. It seems like his entire game is sped up as well looking for this slider, as Trea has abandoned his once disciplined approach towards a curveball that has been deathknell of so many of his at bats.

Now is this all the slider's fault? Is Kevin Long meddling with approaches that have ignored this oft difficult pitch to handle? Who the hell knows. All that is certain is that the Phillies stars' hopes rest on mastering not discipline of the slider, but discipline of approach. If they can't find balance in how they act towards pitches, then our playoff hopes will grow ever slighter.


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