Spencer Turnbull Has a Sneaky Fastball

It was never going to be a fun year to be a Detroit Tigers fan. The hundred losses could tell you that, or the fact that the team’s lone All-Star was reliever Shane Greene, who now plays for the Braves. The joy in Tigers fandom was concentrated in the minors this year; in top prospect Casey Mize’s polish, in Matt Manning’s production, in Isaac Paredes showing he was ready for Double-A.

But the major league team wasn’t without its bright spots. Greene performed well enough to net two interesting prospects in a trade, Niko Goodrum scratched out a 2-WAR season, and Matthew Boyd had a first half so nice that the Tigers asked for the world in trade (they didn’t get it). In addition to those major leaguers taking a step forward, there’s one other Tigers performance to get excited about: Spencer Turnbull has quietly been an above-average pitcher in his rookie season.

There were signs that Turnbull could hack it in the major leagues before this year, but nothing decisive. He used his sinker/slider starter kit well in Double-A in 2018, racking up a 25% strikeout rate and 3.16 FIP over 100 innings of work. That sounds excellent, but the hidden downside of performing well in Double-A is that you’re pitching in Double-A rather than the big leagues. Turnbull was 25 then, older than the average age for the league and way past when most top prospects move on.

Still, good pitching is good pitching, and the Tigers were desperate for whatever they could get. After a single dominant outing in Triple-A, where he struck out 7 of the 13 batters he faced, Turnbull was summoned back to the major leagues, where he had had a brief previous cameo as a September call-up.

Rather than the same sinker-heavy pitcher he was last year, Turnbull revamped his pitch mix over the winter. His sinker, which he’d thrown about half the time, became more of a complementary pitch, replaced by a four-seam fastball he’d previously only dabbled with. The new pitch acted like a hybrid in the best possible way, generating a 76th-percentile whiff rate and an 83rd-percentile groundball rate.

How can it achieve those two goals? Essentially, the pitch moves unlike any other four-seam fastball. It has less rise and less fade than almost any other four-seamer in the game despite above-average spin. That can only happen with a ton of gyrospin, which is unique among four-seamers. Batters can’t pick up the pitch, which fades much less than a sinker but rises less than a four-seamer. They’re topping it, swinging through it, fouling it off — a bevy of bad outcomes for hitters.

And we can offer a more quantitative explanation than “it looks like batters don’t see the pitch well.” The worst outcome for a pitcher is for the batter to barrel up the baseball. This happens on 3.2% of swings against four-seam fastballs league-wide, and it doesn’t end well for the pitcher. Batters are hitting .807 with a 2.805 slugging percentage on those balls.

Luckily for Turnbull, he simply doesn’t allow barrels. Here are the 10 pitchers with the lowest rate of barrels per swing on their four-seam fastballs (minimum 500 fastballs thrown):

This list is a combination of interesting and dominant. Some of the best pitchers in baseball are on there, as are two of the most deceptive. Lauer and Means get by without overwhelming velocity, and their ability to miss the barrel of the bat helps explain why. Turnbull is kind of doing that, but he’s using his plus velocity to get whiffs as well, something neither Means nor Lauer excels at.

Maybe you’re a visual learner. Take a look at this Jurickson Profar swing:

That pitch was hit for a single, but that’s the kind of contact a pitcher would take every day of the week. Soft, on the ground, and to the pull side? Where can I sign up?

It’s not all soft contact, of course. Eloy Jiménez looks downright uncomfortable while swinging through this fastball:

It almost seems as though he thought the pitch was going to sink and fade towards him, as if he read sinker out of Turnbull’s hand and couldn’t adjust enough mid-swing to get back on the pitch. Turnbull’s delivery, with its loopy motion on the way to the release point, surely has something to do with it, but the ball’s odd movement profile no doubt helps as well.

There’s more to pitching than a wicked fastball, and Turnbull still has work to do on that front. His main secondary pitch, a cutter/slider hybrid he throws 20% of the time, is at sixes and sevens, not quite hard enough to mimic Jacob deGrom’s hard slider with not quite bendy enough to look like Adam Ottavino’s frisbee either.

The end result is a pitch that doesn’t help Turnbull as much as it should. Against lefties in particular, it falls flat, caught somewhere in between running in off the plate and dropping off the table low. The location is the real problem, as is the case with lots of so-so pitches. Leave a slider without much break here, and bad things will happen:

The KDE graphs can mislead, but in Turnbull’s case, they capture the basic idea. He bounces 17.8% of his sliders, in the top 10 in all of baseball, while also leaving too many over the plate. Because the pitch doesn’t have a ton of movement, he only gets swings on 31.8% of his out-of-zone sliders, in the bottom 25 percent of all sliders. The combination of too many sliders left over the plate and not enough swings at bad pitches leads to poor results, despite scouts thinking the pitch has a chance to be good if Turnbull can harness it more effectively.

The pitch can absolutely work; don’t get me wrong. When located well, it’s hard to deal with. Take a look at this slider that Curtis Granderson simply can’t handle:

But too many of them are either taken for balls or end up spinning over the middle like this:

To complement the lively fastball and slider, Turnbull features a changeup that he throws almost exclusively to lefties. It’s a Greinke-style hard change, with about 7 mph of separation from his fastball, and tails away from lefties like a banshee. The changeup will probably never advance past a pitch he uses to get lefties out, but with his fastball, he doesn’t need it to be anything more. He also dabbles with a sweeping curve, though he’s used it less and less as the year has gone on.

All of these mixed secondary pitches don’t take away from one simple fact: Spencer Turnbull’s four-seam fastball is one of the best in baseball. Some combination of spin, speed, and deception make it one of the hardest fastballs to make contact with, let alone square up — impressive from someone who was a sinker-first pitcher in Double-A last year. That alone is reason enough to keep running him out there, to see if he can unlock another level of performance through repetition.

Maybe Turnbull won’t ever develop his slider or curveball enough to have a reliable second pitch. Maybe an offseason of video scouting will help batters cope with his unique fastball and he’ll need to make another adjustment. That uncertainty, that potential, is exactly what the Tigers were hoping for when they brought Turnbull up.

Where last year they had a 25 year old coaxing grounders out of minor league bats, this year they have unmolded clay, a pitcher who could be a lights-out reliever or a middle-of-the-rotation starter with one subtle change in approach. Could this year be his high water mark? Sure! Could the lack of command catch up with him? No doubt. That’s fine, though — the Tigers have the luxury of giving pitchers like Turnbull enough starts to find out what will happen, and he’s rewarded them with an intriguing season.