A few weeks ago at Prospectus, I looked how many left-handed and switch-hitting batters are projected to start for each team across the divisions. Perhaps unsurprisingly, the American League East had the highest percentage of non-righty batters. This means right-handed pitchers incapable of getting lefties out should not start or have roles wherein they are asked to pitch to multiple lefties in close situations. Employing a defined closer means running the dude out for the ninth inning in close games (but only three runs or fewer, four and it’s not a save situation and a totally different ballgame) and having him pitch to the opposition regardless of the platoon split involved.
Combine those two thoughts and you can see where this is heading. Joel Peralta has utility. He’s skilled at retiring righties, but his career numbers against lefties are woeful (.271/.345/.525). Now, maybe he discovered the trick to getting them out last season (.212/.278/.318), but there’s no guarantee and no reason to assume last season is the appropriate baseline from which to work. For now, Peralta should be used mostly against righties, if not to the extremes of Dan Wheeler (although, if his career holds true, then yeah, he should never see a righty in a moderate-to-high leverage spot if at all avoidable).
Joe Maddon cannot control who faces Peralta, but he should have an idea based on the upcoming batters. Dustin Pedroia and Derek Jeter are unlikely to be pinch hit for, but opportune matchups like Mike Cameron will be flipped into undesirable faceoffs with J.D. Drew, Jacoby Ellsbury, or whichever left-handed batter is sitting in favor of Cameron. Flexibility and foresight is king when it comes to lineup decisions, so just as Maddon keeps one eye on the present and one eye on the future while his team bats, he too must take this approach while his team pitches.
For those reasons, Peralta is a horrible choice as a fulltime closer or eighth inning guy or just about any designated role that is oblivious to the context of which batters are due up. Ultimately, reasons like this are why designated roles are overrated. The comfort they provide to the pitchers is equally felt by tactical-savvy managers capable of turning the tables in a blink of the eye against non-elite relievers. Everyone is so concerned about who gets the saves that keeping the lead is taken for granted.
(H/t to Sternfan for the inspiration)