Hardly a week goes by when you don't see a manager or coach quoted as saying that reliever pitch best when they "know their roles." It has long ago passed into the conventional wisdom, not only as a defense for the traditional use of the closer, but for much more than that.
Managers use it to explain why they designate certain relievers as 7th or 8th inning guys, or why one LOOGY comes in in the 6th and the other in the 8th, or why some guys don't pitch when their team isn't in the lead.
This, of course, drives some (most?) sabermetricians crazy. We tend to think that the best pitcher ought to appear in the most highly-leveraged situations, period. Mariano Rivera ought to appear in the 6th inning sometimes, and it's a-ok to use a mediocre reliever in the 9th inning with a three-run lead.
But this "knowing your roles" business is outside of the sabermetrician's purview, and I tend to think it's garbage. Or at least it should be. If a high-priced reliever comes into a game in the 7th thinking to himself, "damn, my manager doesn't value me like he should," or "damn, this is really going to hurt during my arby hearing," that's a sign of bad managing of personnel, or that the reliever isn't as good as we may think.
The reason I bring this up, though, is that I thought of an alternative explanation today.
The idea behind this concept, usually, is that the relief pitcher performs best when the relief pitcher knows his role. Jon Papelbon can chill out until the 7th, and probably the 8th inning, every night, without fear of being pressed into service. On the other hand, in a close game, a mediocre long man can tune out.
But maybe that's not true. Maybe the relief pitcher performs best when the manager knows the pitcher's role.
Here's why this may be the case. I think it's safe to say that relief pitchers perform best when they are sufficiently well rested. (Yes, I know that begs a whole series of questions.) There hasn't been enough research done on this, partly because some of the data isn't available. "Well-rested" hinges on many variables: number of innings pitched in a variety of time spans, number of pitches thrown, number of pitches per inning, number of times warmed up, and perhaps some other stuff too.
That last variable is the important one. A friend pointed out to me that, in the Rockies-Padres tiebreaker a couple of weeks ago, Trevor Hoffman had warmed up three times when he finally got into the game. Since Hoffman is a closer, and usually a one-inning closer, I'm guessing that's exceedingly rare for him. He pitched badly, and the Rockies appear headed to the World Series.
That's anecdotal evidence, of course, but I'd be willing to bet that one warm-up is better than two, two is better than three, and so on. While some relievers are surely more flexible than others, and some (especially OOGYs, I'd imagine) are forced to become more flexible, any pitcher is likely to be at least a little better when he has warmed up less.
The stricter the roles, the fewer warm-ups per appearance. I'd bet that a closer with an old-school manager probably appears 90% of the time he warms up. But on the flip side, a different middle reliever on the same team may appear less than a third of the time he warms up. Every team seems to have one or two pitchers who always seem to be the first out of the pen, and their managers aren't afraid to get them up over and over again.
If you go to a closer by committee, or even something in between the closer by committee and the very strict role-based bullpen system, you get fewer appearances per warm-up.
That has several ramifications. As in the Hoffman example, the pitcher may be more tired by the time he comes in. Not only is he possibly less effective, but even if he is effective, he may not be able to last as long. The effect compounds, as well: the more the reliever warms up, the more tired he may be over the course of the week, especially if his manager isn't sensitive to the dangers of continually warming him up and sitting him down.
As you may have noticed, I'm forced to hedge a lot to talk about this. Frustratingly, this is one area where I don't think we have any data. To begin to analyze issues like this, we'd need to track who gets warmed up, when, for how long, and how many pitches they throw. It wouldn't hurt to know which pitchers work the hardest in the bullpen, though that's of course much harder to measure.
Is it worth starting a project to have fans of all 30 teams watching games and measuring these the best they can? I don't know. It certainly is an area that demands more attention, if only to evaluate some of the more common conventional wisdom claims of managers and coaches. It may help explain why some relievers get so much better when they are anointed closer, and it may provide some useful tips for managers to keep their pitchers sufficiently well-rested, perhaps while also taking advantage of some of the benefits of a more flexible bullpen.