For me, one of the most memorable pitches of the past few seasons is the fastball that Sergio Romo threw by Miguel Cabrera to clinch the 2012 World Series. On its own merits, Romo’s fastball isn’t particularly good, and for that reason, everybody watching figured Romo would throw a slider. For that reason, Romo threw an effective fastball, and it was the biggest pitch of his life — and it turns out every pitch is connected and one never has to really stand on its own merits. Romo succeeds with his fastball in the way that Tim Wakefield succeeded with his fastball: He uses the pitch to take batters by surprise, because his primary pitch is way better.

Game theory is a complicated concept, but pitch mixes make it simpler to grasp. Say you have a pitcher with an unbelievable changeup. Even though the changeup is his best pitch, it wouldn’t make sense to throw it 100% of the time, because a key component is surprise. Therefore there exists some optimum frequency with which the pitcher would throw something else, even if “something else” is something a lot worse. Because of the changeup, in theory, it wouldn’t look a lot worse in context. A hitter should never be able to know what’s coming, unless the pitcher is Mariano Rivera, who now is retired.

And this brings us to the current matter of Al Alburquerque, who has a slider. He has a very good slider, and he’s thrown it a whole bunch.

The Tigers would like for him to throw it less. From pitching coach Jeff Jones:

“Part of the problem is his slider is so good,” Jones said. “If you have a pitch nobody can hit, it’s difficult not to throw it every time the catcher puts the signal down.”

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Jones said the Tigers spoke to him last year about using his fastball more, and will do so again this spring.

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But sliders, Jones noted, are harder to throw for strikes and harder on the arm.

We can’t speak too much to the injury risk. Alburquerque has already had elbow problems, and it’s been suspected for quite some time that there’s a relationship between slider usage and developing arm issues. No matter what, Alburquerque will always be a high-slider pitcher, barring some sort of life-changing, mid-career epiphany.

We’ve got pitch-type information going back to 2002, and since 2002, just setting a minimum of 50 innings, Alburquerque’s 61% slider rate comes in first. If you split the seasons and set a minimum of 40 innings, then Alburquerque’s 2013 ranks fifth, at 65%. He’s between Michael Wuertz‘s 2009 and Carlos Marmol’s 2011. Alburquerque is among the most extreme slider pitchers, probably ever, and based on that alone it stands to reason he could probably throw the slider a bit less. But then, here are some of them, from the same game last season:

I don’t know if those are particularly remarkable examples of the pitch. They’re more like representative examples of the pitch, which has been among the most unhittable pitches in baseball over the years, in the company of pitches like Ryan Madson‘s changeup and Brandon League’s splitter and Jonny Venters‘ curveball. Just about half the time, batters have swung at Alburquerque’s slider. More than half of those times, the batters have whiffed. It’s the same for both lefties and righties, so it’s not like Alburquerque has run some horribly lopsided platoon split. He’s fallen in love with his slider because his slider has been amazing.

Rather unsurprisingly, hitters have come to somewhat expect Alburquerque’s slider. This is reflected by the reality that Alburquerque’s fastball has shown an incredibly small swing rate against, around 32%. It’s a pitch that’s taken hitters by surprise, but then, it’s a pitch that’s been hit nine-tenths of the time it’s been swung at. Batters rarely chase it out of the zone. When batters have made contact, the fastball’s been punished more than the slider. For a pitch that’s supposed to be a faster change of pace, Alburquerque’s fastball hasn’t helped him very much.

Additionally, it’s true, what Jones says: It’s generally easier to throw fastballs for strikes than it is with sliders. Alburquerque, sure enough, has a higher fastball zone rate than slider zone rate. But then, overall, 65% of his sliders have counted for strikes, in large part thanks to swings out of the zone. Just 56% of his fastballs have counted for strikes, in large part thanks to fewer swings out of the zone. And it’s not like Alburquerque is a guy with pinpoint command, so his fastball zone rate is still below 50%.

The suggestion there is that Alburquerque’s fastball could be a weapon, and that by throwing the fastball more, he could also make his slider more effective. What the numbers show is Alburquerque’s slider is already ultra-effective — and from a performance standpoint — he should throw it more often, since his fastball hasn’t been real good, even as a relative rarity. We have PITCHf/x record of 69 Alburquerque hits allowed, and 36 have come against his fastball, even though it’s been thrown far less often. It would be one thing if his fastball were better; that is, if he had better command of it. Failing that, Alburquerque’s done well to favor his breaking ball to such a ridiculous extent.

It’s perfectly valid to be worried about Alburquerque’s health, given the history of slider-throwers and given his own history. The Tigers know more about that than I ever will. For that reason alone, Alburquerque might consider cutting back some, to partially reduce his own risk. But he’s always going to throw a lot of sliders, since he has an elite-level slider, and he’s always going to be around a similar risk level. And while you might suggest throwing more fastballs could lead to quicker plate appearances, it could and would also lead to a higher OBP, so pitches might not actually be saved in the end.

Alburquerque might indeed be best as an extreme slider-thrower in the vein of Luke Gregerson. The data don’t seem to call for more fastballs. If Alburquerque starts throwing a better fastball that would be one thing, but every pitcher would be different if he threw better pitches. What Alburquerque has — what he’s always had — is an amazing breaking ball that confounds hitters on both sides of the plate. It’s a pitch he uses a lot. And it’s a pitch he should use a lot.