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Miguel Montero and the Vagaries of Variance

On Friday afternoon, Miguel Montero’s throw to second base tailed off into center field, allowing the Braves’ Andrelton Simmons to advance to third base. It was the sixth inning of a one-run game, and so I was understandably upset. So upset, in fact, that I lashed out with some ungentlemanly language, using an epithet (#Cubes) that hasn’t been heard around these parts for quite some time. For that, I apologize. Luckily for me, one of my followers rescued the situation with an interesting question:

The probably-rhetorical implied question—When was the last time Montero threw a ball, aimed for second, that didn’t end up in center field?—is easily answered: it was on August 16th, against the White Sox. But the more interesting question is the explicit one: Has Montero always been such a poor thrower? If so, why? If not, why not? I promised to look into it.


Before I take you through a few of the results, it’s worth getting an important note out of the way, and that’s this: We don’t know as much as we’d like about caught-stealing rates. We know that a lot of things interact to drive the numbers a catcher puts up, putatively on his own—the pitcher on the mound, the runner on the base, the catcher’s previous success, the handedness of the batter, and probably much more—but we don’t have a really great idea of to what degree, exactly, each consideration moderates some true talent level that the catcher possesses. We do know that the best catchers, at least in terms of CS%, tend to stay relatively steady year-over-year (though there’s not perfect correspondence) so it’s reasonable to conclude that catcher skill has something to do with CS%. But we don’t know how much.

Anyway. Here we go. First, let’s take a look at Montero’s numbers, relative to the league:

Year SBA CS CS% League CS% CS% – League CS%
2010 47 21 31% 28% +3%
2011 48 32 40% 28% +12%
2012 44 32 42% 26% +16%
2013 31 15 33% 27% +6%
2014 64 26 29% 27% +2%
2015 51 14 22% 30% -8%

The first thing that jumps out is that, yes, Montero’s been quite a bit worse this season than he has been in the past. Not only is 2015 the first season of the last six in which he’s put up numbers below league average, it’s his lowest mean CS% of the sample as well.* So there’s something to Bobby’s observation that Montero seems to be worse this year than he has been before: he has been worse. Worth noting here: Alongside Harry Pavlidis, BP’s Stats Director, I’ve reviewed one of BP’s soon-to-be released advanced catching metrics, and while it is generally in agreement with straight CS% about Montero’s decline this year, it’s also less impressed by his past work than these numbers indicate.

But more on that when those metrics are released. The other thing that stands out at me is that Montero’s numbers keep jumping around. Here’s the same chart, with the first two and final columns removed, and two additional columns added—the absolute value of the deviation in Montero’s CS%, and in the league’s CS%:

Year CS% abs_dev(CS%) League CS% abs_dev(lCS%)
2010 31% - 28% -
2011 40% 9 28% 0
2012 42% 2 26% 2
2013 33% 9 27% 1
2014 29% 4 27% 0
2015 22% 7 30% 3

While the league’s numbers have held pretty steady year over year (which you’d expect, given the much larger sample size), Montero’s numbers have jumped all over the place: up nine points between 2010 and 2011, down nine points again between 2012 and 2013, and down seven more points between this year and last. Add up all those deviations, and divide by the sample size, and you get a mean deviation (since 2010) of 6.29 percentage points. That’s a quite a lot, and it means that we shouldn’t really be shocked if we see Montero’s 2016 CS% anywhere in a band between about 15.5 percent and 28.5 percent.

But the crazy thing is, Montero’s mean deviation isn’t all that dramatic compared to the rest of the league. While catchers as a whole are pretty consistent in throwing out about 27 percent of batters, year over year, individual catchers’ performance fluctuates wildly between seasons. I asked BP’s Rob McQuown to pull some numbers, and he did. Here’s one for you: Since 2010, among catchers who allowed at least 20 stolen bases in two or more seasons, the mean CS% varied by an average of 8.18 percentage points. So Montero is actually somewhat more consistent than the average everyday catcher.

I can’t take you all the way here and not tell you who the catcher with the wildest swings in CS% is, so here’s that chart:

Catcher avg_CS%_Y1 avg_CS%_Y2 avg_dev
Craig Tatum 7.41 28.57 21.16
Ivan Rodriguez 34.38 52.00 17.63
A.J. Ellis 34.70 38.34 17.61
Anthony Recker 20.59 37.04 16.45
Joe Mauer 22.00 31.69 16.14

Whew! To be fair to Craig Tatum, the offending sample size was just one pair of years: 2010 and 2011. In the former, he threw out seven percent of batters; in the latter, 29 percent. Not a bad year-over-year improvement. For a more honest appraisal, let’s include just the catchers who had at least three season-pairs in the sample:

Catcher avg_CS%_Y1 avg_CS%_Y2 avg_dev
A.J. Ellis 34.70 38.34 17.61
Joe Mauer 22.00 31.69 16.14
Brayan Pena 32.46 27.06 12.89
Kelly Shoppach 31.71 36.73 11.68
Ryan Hanigan 37.18 37.84 11.51

Still pretty darn dramatic, if you ask me. A.J. Ellis’ caught-stealing percentages since 2010: 28, 27, 33, 44, 25, 45. Pretty big jumps, though dragged up by huge deviations over the past four seasons. Anyway, on to the most consistent catchers—those with the smallest deviations between their CS percentages year to year. Here, again, I’ve limited things to the catchers with at least three season-pairs in the sample:

Catcher avg_CS%_Y1 avg_CS%_Y2 avg_dev
Matt Wieters 35.77 36.89 3.55
Jonathan Lucroy 25.42 25.85 3.76
Jose Molina 33.85 29.93 4.30
George Kottaras 15.87 19.32 4.43
Buster Posey 31.76 34.71 4.49

Interestingly (at least to me), we have here a list of catchers with good defensive reputations. That suggests that for these catchers, throwing batters out is a skill that they’ve developed consciously, and that they therefore fluctuate only modestly around whatever their true talent level is. For the catchers on the lists above, in contrast, throwing runners out is really a game of chance; they do well some years, and poorly in others, and are at something of a loss to explain why.


I haven’t made a revelatory breakthrough on the order of discovering a new element here, but I have discovered something interesting: catchers with better defensive reputations tend to be more consistent year-to-year in their ability to throw out major-league baserunners. I could see a case for the causation running either way. Maybe catchers who are consistent are more praised by their peers? Maybe, on the other hand, catchers who are more praised by their peers for other defensive qualities are also good at throwing out runners? I don’t know. Catching is sort of the black box of defensive knowledge. There’s so much to learn, and with (#teasealert!) the new stats BP will be rolling out soon, there’ll be a lot of new ways to do it. For now, at least, all I can say is this: consistency, and metrics surrounding it, might be a good place to start. Oh, and Miguel Montero needs to work on his throwing arm.

*Although not the lowest of his career: he threw out just 21 percent of batters in 2008.

Thanks are due to Harry Pavlidis and Rob McQuown for their help on this piece.

Lead photo courtesy Jake Roth—USA Today Sports.

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2 comments on “Miguel Montero and the Vagaries of Variance”

Tom K

Could the fluctuations just be that runners are more likely to go against catchers that aren’t known as good defensively? With all of the different variables factoring into throwing a runner out, it would make sense to me that luck could play a big role in someone with a fringe ability to throw out runners. Partnered with an above average take off rate, could that explain the huge swings? I think it would be worthwhile to include the takeoff rates in the charts, put those new stats to work. Great work!

Rian Watt

Definitely something to consider, and I like the line of thinking. I’m working on an expansion of this piece for the main site (pending approval by editors), and I’ll explore this avenue there. Thanks for the kind words!

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