Sox Bullpen: The "Need For a Lefty"

"The purpose of a LOOGY is straightforward: he's brought in to face, if not a single dangerous left-handed hitter, then at least a part of the lineup containing a key lefty, or two or more lefties. Very often this is in a fairly high-leverage game circumstance, rarely before the fifth or sixth inning. Sometimes LOOGYs are deployed in the ninth, but rarely are they used in Save situations. Very rarely are they left in for much more than a single inning.

LOOGYs are selected for the role primarily on the basis of their particular effectiveness against left-handed batters -- or, to be less kind, on the basis of their particular ineffectiveness against right-handed batters. They're often long and lanky types, with snaky sidewinding deliveries.

1. A basic precept of the rules of baseball has a huge bearing here: a relief pitcher entering the game is required to face at least one batter to the conclusion of the at-bat, but the offensive team is allowed to pinch-hit at will. What this means is that, while a LOOGY is almost always brought in to face a left-handed batter, the offense frequently responds by pinch-hitting a right-handed batter. (Another basic fact of life is relevant here too: most batters, like most people, are right-handed.) What this means is that LOOGYs in practice don't actually face only left-handed batters. Even the most extreme of hard-core LOOGYs face a significant proportion of righties, and overall, most LOOGYs face right-handed batters most of the time. (Mike Myers, the hardest of Hard-Core LOOGYs, with 0.61 innings/appearance over his 684-game career through 2004, has faced 48% right-handed batters, and the percentage is much higher than that for nearly every other LOOGY.)

It is the case that no category of southpaw pitchers enjoys the platoon advantage more frequently than LOOGYs. But it must be acknowledged that even though the LOOGY is a role designed entirely as a means of exploiting the platoon advantage, it does not do so, to a very great extent of the time.

2. LOOGYs as a group are not especially effective pitchers, as measured by ERA+ or WHIP. Clearly there are two key factors contributing to this: one is the selection bias determining the LOOGY population; the best left-handed pitchers are not deployed as LOOGYs. The other is the fact that even though LOOGYs face a high proportion of left-handed batters, a high proportion of those left-handed batters are the elite left-handed batters in baseball.

So, even though their usage pattern provides them with the best possible conditions -- high proportion of platoon advantage batters faced, and extremely short stints, necessitating no pacing and exacting no in-game fatigue -- it would be unrealistic of us to expect LOOGYs to be really shutting their opponents down. Nonetheless the bottom line remains: LOOGYs don't really shut their opponents down. Even the very best LOOGYs, the elite deployed in the most extreme hard-core pattern -- the Myers, Plesac, Orosco class -- don't produce rate stats that compare with those of the elite pitchers deployed in the more challenging roles of Closing or Starting. And, especially as the number of pitchers deployed as LOOGYs mushrooms, the typical LOOGY is less and less accomplished, resembling an elite pitcher less and less. The LOOGY is a class of pitcher deployed in a very high proportion of high-leverage situations, but without a particularly impressive record of effectiveness."