Johnny Cueto’s Unhittable Fastball

Last night, Johnny Cueto dominated the Dodgers, punching out 12 batters in just six shutout innings. This wasn’t anything new, though; Cueto has been destroying opposing hitters all season long. Hitters are batting just .158/.218/.261 against him this year, good for a pitiful .217 wOBA, and he’s the easy early frontrunner for the NL Cy Young Award.

Cueto has been very good before, but this year, he’s taking things to another level. His 28% strikeout rate is nine percentage points higher than his career average, and seven percentage points better than his career-best, posted last year. Last night was his fourth start of the season in which he punched out 10 or more batters; he’d only done that three times in his entire career prior to 2014. Cueto has always been a strike-thrower with a roughly average strikeout rate who succeeded by limiting hits on balls in play, never walking anyone, and completely shutting down the running game with the game’s best pickoff move.

Cueto is still doing all those things, only now, he’s also posting the fourth highest K% of any starting pitcher in baseball; the only guys ahead of him are Strasburg, Darvish, and Tanaka. Combine an elite strikeout rate with everything else Cueto does well, and you have something close to perfection.

But this isn’t the amazing part. The amazing part is how he’s doing it.

Cueto has thrown 435 pitches this year that the PITCHF/x algorithm has classified as four-seam fastballs. While that only accounts for 29% of his total pitches, it is the largest bucket of any pitch type, as he mixes his pitches about as well as any pitcher in the game. 67 pitchers, Cueto included, have thrown at least 400 four-seam fastballs (per the F/x algorithm) this year. The average wOBA allowed on those four-seam fastballs is .342. Johnny Cueto’s wOBA allowed on his four-seam fastball this year? .147.

Let me put that in some context for you. Here is a graph of the four-seam wOBA allowed for every pitcher with at least 400 four-seams thrown this year.

Cueto’s wOBA allowed on his four-seam fastball is nearly 100 points lower than the next lowest pitcher — Kansas City’s Danny Duffy — and 130 points lower than the third lowest pitcher. One standard deviation for this population is 48 points of wOBA; Cueto is 195 points of wOBA away from the average. That is four standard deviations from the mean. He’s two standard deviations away from the next guy.

Now, wOBA allowed for a specific pitch type isn’t actually the best to evaluate the quality of that pitch, because wOBA is only calculated for balls-in-play or walks, strikeouts, and hit batters. All of the pitches thrown that simply move the count in the pitcher’s favor don’t get counted in wOBA (or any outcome metric), so a pitcher who frequently uses a pitch to go from 1-1 to 1-2 won’t get credit in these kinds of numbers, even though getting into pitcher’s counts is a huge part of being successful. What you really want is linear weights per pitch, which takes into account the results of every pitch thrown and the change in value based on the count it was thrown in.

Thankfully, we have just such a stat. Here is the same chart as above, only based on the run value of each four-seam fastball thrown this year for those 67 pitchers. To account for different usage levels, this is runs above (or below) average per 100 four-seam fastballs thrown.

Cueto is pushing +3 runs per 100 four-seam fastballs; no one else is over +2 runs. In fact, no other starter in the PITCHF/x era has ever been over +2 runs per 100 four-seam fastballs. The results that Cueto is getting on his fastball are just unprecedented.

But, as we’ve been preaching for years, you shouldn’t just judge a pitcher on his results, and there’s no question that a large part of the crazy wOBA and run value numbers for Cueto are driven by his absurdly low BABIP. Cueto has allowed just a .167 BABIP on four-seam fastballs, and since these numbers are not fielding independent, he’s getting 100% of the credit for these outs on balls in play. You don’t need to be an apostle of FIP to guess that a .167 BABIP probably isn’t entirely Cueto’s doing, and won’t continue going forward.

But let’s be clear; this isn’t just a BABIP thing. In fact, we can highlight Cueto’s fastball dominance without ever mentioning a ball in play. For instance, let’s just look at rate of contact on pitches in the strike zone. Z-Contact% is one of the better measures of just the dominance of stuff, as getting hitters to swing and miss at strikes can only really be done with pretty great pitches. As you might expect, the in-zone contact rate on four-seam fastballs is very high; a mean of 88% and a median of 89%. As a basic rule, in-zone fastballs generate contact.

Unless Johnny Cueto is throwing them. Opposing hitters are making contact on just 78% of their swings at Cueto’s four-seam on pitches in the zone, which is easily the lowest of the 67 pitchers with 400+ four-seams that we’ve been looking at. Michael Wacha is second at 81%. During the PITCHF/x era, there have been 493 pitcher seasons in which at least 1,000 four-seam fastballs were thrown; only two of those 493 have resulted in a Z-Contact% below the 80% line. If Cueto could sustain this rate of contact on in-zone fastballs, it would be the lowest ever posted in the PITCHF/x era.

The numbers Cueto is getting from his fastball just don’t even make sense. 70% of the four-seam fastballs he’s thrown have been in the upper half of the strike zone, but when hitters put the pitch in play, it generally results in a ground ball (52%). Four-seam fastballs do not generate ground balls — the average GB% for the 67 pitchers four-seams we’ve been looking at is 39%, and the median is 38% — and no one really gets ground balls on pitches up in the zone.

There’s Cueto, though, pounding hitters up in the zone with fastballs, combining the lowest in-zone contact rate with the 6th highest ground ball rate on his four-seam fastball. And when hitters do hit his four-seam in the air, it’s not going anywhere. 35% of the fly balls the pitch has generated have stayed on the infield; that’s also the sixth-best total for that pitch in all of baseball.

If you were to rank the outcomes you’d want for a pitcher on any given pitch that a hitter decided to swing at, it would probably go something like this:

1. Swinging Strike
2. Infield Fly
3. Ground Ball

Those three events are basically all hitters are doing against his four-seam fastball this year, and the result is that the pitch has allowed just 10 hits, and nine of them have been singles. He’s the only pitcher in baseball with 400+ four-seam fastballs thrown and no home runs allowed. The only other pitcher to only give up one double on his four-seamer this year is Colin McHugh, but he’s also allowed three home runs on the pitch.

To be honest, I can’t give you a reason for why Cueto has been able to do this. The best guess I could make is that his delivery is particularly deceptive, and hitters just aren’t picking up the ball until it’s too late. There’s nothing that really stands out in terms of velocity, movement, or location that would suggest that Cueto’s four-seam fastball should be essentially unhittable. But for the first 14 starts of the season, that’s exactly what it’s been.