What’s behind Trevor Story’s sophomore struggles?

Before suffering a season-ending thumb injury last year in his rookie season, Trevor Story was crushing baseballs with regularity. In 415 plate appearances, he posted a .272/.341/.567 triple slash with 27 home runs and a 120 wRC+. Less than a year removed from the fiercely debated Troy Tulowitzki trade, it seemed like perhaps the Rockies had found their next franchise shortstop.

Healthy to begin 2017, Story came into the year hoping to remain that way and prove 2016’s production was not a fluke. He’s done well to stay on the field, but the offense that excited Rockies fans in his rookie season has been lacking. In 336 plate appearances, Story has hit just .234/.310/.436 with 15 home runs and a 76 wRC+. He hasn’t lived up to 2016’s home run rate, but the power’s still there, as his 17 percent home-run-to-fly-ball percentage is above league average. That 76 wRC+, though, that sticks out like a sore thumb. Other than maintaining solid power, Story hasn’t been the same this season.

Remember True Detective? The hit HBO series starring Matthew McConaughey and Woody Harrelson in season one but not season two? That’s Trevor Story. One minute you’re glued to the screen watching McConaughey wax poetic about the meaning of the life while solving a complicated murder-mystery in the Louisiana Bayou. The next you’re watching Vince Vaughn do... whatever it is he did in season two, I’ll be honest, I bailed halfway through.

So, what’s the story deal with the Rockies’ young slugger? Let’s take a look at some important offensive markers to see if we can pinpoint what has gone wrong.

First, let’s determine if anything drastic has changed in Story’s batted ball profile. In these times of “elevate and celebrate,” maybe he’s struggled by hitting the ball on the ground this year, which could explain his issues.

Nope. Story is still putting the ball in the air at nearly the exact rate he did in 2016. He’s traded a few percentage points between his line drive and ground ball rates, but nothing to be overly concerned about. Now, while his fly ball rates are nearly identical in both this year and last, the 6.7-percent drop in home run-to-fly ball rate and the 4.8-percent increase in infield-fly rate are both troubling and due in part to the fact that Story is simply not hitting the ball as hard this season.

Chart via FanGraphs

Story’s hard-hit percentage has fallen considerably, from 44.9 percent to 37.2 percent to be precise. Thanks to the FanGraphs splits tool we can see that the decline is even more severe on fly balls (the batted-ball type that is most dependent on quality of contact), where his hard hit rate has gone from 52.6 percent to 40.2 percent.

According to Statcast, his overall average exit velocity has dropped from 90.2 miles per hour to 89.3, and his average launch angle has increased from 16.7 degrees to 20.1. That squares with everything we’ve seen. Story is still hitting flyballs, but they’re not as hard and more of them are pop-ups, which are basically guaranteed outs.

Let’s move on to Story’s plate discipline.

There are some differences, but nothing jaw dropping, right? Story is swinging at nearly the same rate this year and has even cut down on his swings outside of the zone a little. His contact rate has fallen by four percentage points which isn’t ideal, but more outside of the zone than not, which is somewhat preferable, since contact outside of the zone tends to be bad contact. His swinging strike rate has increased, which, alongside the decrease in contact rate, explains the 4.1-percentage point increase in strikeout rate.

The decrease in contact rate combined with the increase in swinging strike rate is the most problematic aspect of Story’s plate discipline this year, so let’s go deeper and look at what pitches are giving him the most trouble. First, how has his swing rate changed against different pitch types?

Chart via Brooks Baseball

Story is attacking offspeed pitches and laying off breaking stuff. Let’s check out this exact same Brooks Baseball chart but with whiffs instead of swings. How’s the aggressiveness against offspeed pitches working out for him?

Chart via Brooks Baseball

Oh, that’s not great.

Story’s swinging strike rate against offspeed pitches has gone up more than 10 percentage points, and even though he’s not offering at breaking stuff as often, he’s whiffing more against them as well. Since Brooks Baseball’s “offspeed” category includes only changeups, splitters, and screwballs, we can basically interpret “offspeed” as a proxy for changeups. (Splitters are still around but aren’t all that common, so we can focus in on the cambios safely.) Story’s contact rate on the pitch has gone down over 20 percentage points and his whiff rate up by nearly 10 percentage points, and it seems to be because he’s not getting hittable changeups anymore.

Charts via Baseball Savant

Opposing pitchers are doing a much better job keeping their changeups down and on the outside corner. Story’s wOBA against the changeup is nearly identical — .302 in 2016 and .301 in 2017 — but his isolated power on the pitch has suffered greatly; down to .136 from .226 last season.

By breaking down individual pitch type numbers we are traversing in some serious small-sample size territory, but since we’re here let’s inspect more than just Story’s work against changeups. That can’t be the only pitch he’s had trouble with this year.

Data via FanGraphs

While Story’s numbers against the changeup are definitely worse, it’s not even close to his decline in production against four-seam fastballs, sliders, and cutters. The downturn against four-seamers can be partly attributed to a decrease in BABIP on the pitch from .393 to .304, and his problem with cutters can be traced to a 32.3 percentage point increase in ground ball rate against the pitch.

Story’s issues with the slider are much more interesting. Unlike the changeup, opposing pitchers are throwing more sliders in the zone against him, but against them he’s seen a sharp decrease in contact rate and an increase in swinging strike rate. Whereas Story had eight home runs against sliders in 2016, he’s hit only one out of the park in 2017. There is a clear difference in what type of sliders he is swinging at this season.

Zone Charts via FanGraphs

Last year Story was susceptible to the low and away slider — as most batters are — but otherwise he only offered at the pitch if it was in the lower part of the zone, and preferably middle-in. In 2017 he’s chased less at sliders low and away, but has totally lost the bottom of the zone against the pitch. He’s swinging at low sliders at a much higher rate, and if the pitch is in the zone, he’s more likely to offer if it’s away.

While pitchers have by and large improved location on their changeups against Story, that’s not the case for sliders. He’s simply seems to have lost the discipline that he showed against the pitch in his rookie season.

It’s important to reiterate that the pitch-type numbers stem from small samples and can easily change with more plate appearances, which only serves as a reminder that Story isn’t necessarily doomed. They are true to this point and explain how Story has struggled. Small samples are worthy of skepticism, and that doesn’t make them incapable of showing what’s happened, but whether they tell us about his future is another question.

Who is the real Trevor Story, the 2016 or 2017 version? As with most things the truth probably lies somewhere in the middle, but it’s going to take more than one simple fix to return to the form of his rookie season. The league has adjusted its approach, and Story has thus far been unable to adjust back.

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All statistics updated through July 29, 2017.

Chris Anders is a featured writer at Beyond the Box Score. You can find him on Twitter @MrChrisAnders.