Middle school students associate the word "loogie" with a big wad of spit laced with mucus. Baseball fans are more familiar with the spelling LOOGY and the acronym for which it stands: Lefty One-Out GuY. This refers to a left-handed pitcher whose sole duty in the bullpen is coming in to retire tough left-handed hitters. While these relievers don't always strictly follow the usage pattern that the LOOGY label would suggest (often they face multiple batters in a game), it's clear what their specialty is.
The Twins have largely relied on two pitchers to fill this role in the 2010 season: Jose Mijares and Ron Mahay. While Mahay has been effective against left-handed hitters, most people (rightfully) do not view him as a particularly reliable option in high-leverage situations so Mijares has been the go-to guy when multiple left-handed hitters have been due up with the game on the line.
Unfortunately, Mijares injured his knee while trying to make a play at first base in last night's game and is headed for the disabled list. Since left-hander Glen Perkins had already been called up to the big-league roster as a spot starter for Wednesday's game, the prevailing wisdom as that he should be moved to the bullpen as Mijares' short-term replacement.
However, this cannot be emphasized enough: Perkins is NOT a candidate to become a left-handed specialist out of the bullpen.
That's because, despite the fact that he throws with his left arm, Perkins has proven over a lengthy period of time that he is simply not an asset against left-handed hitters.
Over 117 innings with Triple-A Rochester this season, Perkins has allowed a .327 batting average against lefty hitters, compared to .305 for righties. His strikeout rate against righties during that span (7.56 K/9IP) has actually been markedly better than his strikeout rate against lefties (4.76 K/9IP).
The trend is not unique to this season. In his minor-league career, Perkins has allowed a .277 average against left-handed batters as opposed to .254 against righties. His K-rate against righties is 8.29 compared to 7.71 against lefties. While his control has been slightly better against left-handers (3.29 BB/9IP to 3.00), the difference is negligible.
Those patterns have also been reflected during Perkins' major-league time, during which he has allowed a .327 average and .857 OPS against lefties, versus a .283 average and .786 OPS against righties. In 286 big-league innings, Perkins has posted a solid 107-to-46 strikeout-to-walk ratio against right-handers, while the ratio against lefties is an ugly 40-to-30.
I'll point out that right-handers have always been able to hit Perkins harder (69 of the 82 home runs he's allowed in his pro career have come against righties), but the statistics make it clear that Perkins is far from dominant against left-handed batters.
With his 6.08 ERA and 1.50 WHIP in Triple-A this year, Perkins doesn't belong on a big-league roster to begin with. But if the Twins are thinking he might be an asset as a lefty specialist out of the bullpen in the absence of Mijares, they're sadly mistaken.
It's just irresponsible to overlook the mounds of evidence suggesting that Perkins is far less effective against lefties than righties, regardless of which arm he throws with.