MASTER NOTES: Spin doctor

Earlier this week, a discussion broke out among a few BaseballHQ analysts about Marcus Estrada, and in particular his ability to maintain a Hit Rate (H%, also expressed as BABIP) well below what are considered pitcher norms of around 30%.

In his first full season in 2012, Estrada had a H% of 29%, certainly right in line with expectations. But then a funny thing happened: Estrada’s H% started falling. In 2013 and ’14, it was 26%. Then last year, 22%. This year, 20%.

We know that individual hitters set their own Hit Rates, but the common wisdom is that pitchers do not. And while that might generally be true, successful fantasy owners are always on the lookout for the outlier, the anomalous guy who is doing something differently and confounding expectations as a result.

So what is it about Estrada? In a word: pop-ups. And what’s behind the pop-ups? In a word: spin.

One of the triggers for the discussion was an article at, in which writer Mike Petriello discusses how spin rate affects batted-ball outcomes. Petriello, who works with the Statcast team at, summarizes that relationship this way: “(H)igh-spin fastballs tend to correlate better with swinging strikes and popups, while low-spin heaters dive and turn into ground balls.”

And it turns out that Estrada gets tremendous spin on the ball. His four-seam fastball averages about 2,400 RPM, and he has even had a few over 2,600 RPM, according to the Statcast data at

What’s more, according to the article, Estrada says the spin on his four-seamer is almost perfectly backwards, like a “cue ball” with full reverse English, or a perfectly driven golf ball with backspin carry and no fade or draw (that’s a slice or hook if you’re not doing it on purpose).

The result is a fastball that stays pretty straight (and therefore controllable) as far as inside-outside movement is concerned, but has more “positive” vertical movement than anyone else in baseball. This doesn’t mean Estrada’s fastball actually rises, but that it drops less than everyone else’s pitches approaching the plate. This creates the illusion of a rising ball, because batters in modern baseball are conditioned to expect a fastball to follow more of a downward path as it nears the hitting area. So when they swing, they tend to get under the ball because they expect it to be lower than it is.

And under the ball? That’s where the pop-ups live.

I checked all the starting pitchers this year (at least 15 starts or at least 10 starts with less than 25% relief appearances). Of the 146 pitchers who made the cut, only Jeff Weaver has more pop-ups than Estrada as a percentage of total batters faced (TBF). The gamewide average for starters is around 2.3% of TBF; Estrada and Weaver are over 6%, the only two pitchers at that level.

Now you might think that none of this matters, but it really does. The pop-up, or infield fly ball (IFFB), is usually lumped in with the other flyballs as part of the standard G-L-F percentage breakdowns widely used in stat packages.

But pop-ups should be in a category unto themselves, because they are not really fly balls in their potential effect on the game. About 24% of flyballs end up as hits, including extra-base hits and HR. Even flyball outs can provide some offensive use, by advancing runners on the bases, including to score on sac flies.

The IFFB, on the other hand, is a hit barely 2% of the time, often in one of those farcical “After you, Alfonse” moments when four infielders stand around gaping at each other while the ball plops to the ground right in the middle of them. Even when that happens—and why is it never scored an error? Don’t get me started—it is unthinkable that a baserunner could advance or score on the play.

In other words, except for its lack of value as a fantasy stat category, a pop-up is pretty much the equal of a strikeout, because both get the out while preventing any other offensive advantage.

If strikeouts and pop-ups are pretty much the same, then maybe we should combine K% and IFFB% (of TBF) to get a clearer picture of a pitcher’s true ability to limit offense.

As the story noted, doing this calculation for the 2016 season to date shows Estrada is the 11th-best SP in MLB this season, despite being only 33rd in K%. And the guys ahead are mostly ace-caliber starters like Jose Fernandez, Clayton Kershaw, Max Scherzer and Madison Bumgarner.

Interestingly, there are also some targetable guys on the list ahead of Estrada as well: Danny Duffy has an above-average IFFB%, and Vince Velasquez is at 4%, to go with a near-elite 27% K%.

All of this said, Estrada does seem to have had an element of luck on his side. His hit rates on soft grounders and hard grounders are half league average, which might be helped by pretty good infield “D” in Toronto. Similarly, his hit rate on hard flies is 15 points under the 48% average, perhaps thanks to Kevin Pillar. And his hit rates on soft- and hard-hit liners are well under league average as well.

Still, there might be something in the numbers that does explain this seemingly random variation from the norm. As noted above, he’s been doing this now for four straight seasons, and actually getting better over that time. We might eventually discover that the “cue ball” four-seamer is generating advantages we don’t even recognize yet.

In the meantime, keep an eye out for pitchers with unusually high pop-up percentages. Especially when those pitchers are outwardly not that interesting, you could be onto a sleeper with tremendous upside.

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  For more information about the terms used in this article, see our Glossary Primer.