Last night, I wrote about the possibility of the Pirates acquiring Nate Schierholtz. The community liked this idea less than I did. Part of my thinking was that 1) right field has been a weakness this season; 2) Jose Tabata is the one right fielder who has played well so far, and he's a righty; and therefore 3) Schierholtz, who has a long history of good hitting against righty pitchers, would be a good player to pair with Tabata.
Tabata himself hasn't had much of a platoon split over his career, posting a .716 career OPS against righties and a .720 OPS against lefties. That doesn't mean a Schierholtz/Tabata platoon would be a bad idea, however. For one thing, Schierholtz has posted a reasonably large platoon split over his career and an even larger one over the past three seasons, when his OPS against righties has been above .800 each time. He's also a better defensive player than Tabata. So Schierholtz/Tabata would, at least on paper, be an upgrade over Tabata by himself.
And this isn't really a part of my argument, but Tabata only has 333 career plate appearances against lefties. As we all know, 333 plate appearances isn't necessarily enough to gauge a player's true skill. Platoon splits take a very long time to regress, and given time, Tabata's splits would likely widen such that he hit lefties better than righties, as is generally the case with right-handed hitters. For more on this idea, see here. The Schierholtz/Tabata platoon concept is primarily based on the idea that Schierholtz would benefit, but if you think Tabata shouldn't be platooned because his career splits are roughly the same from both sides of the plate, I don't agree, in part because it's unlikely Tabata would continue to post those numbers.
Anyway, all the thinking about platoon splits got me to thinking about this: What's the best way for the Pirates to improve against lefties? Schierholtz obviously wouldn't help with that, and probably the Pirates' best approach at the deadline would be to simply worry about improving their offense, and not worry about lefty hitting in particular. The Bucs have run out some ugly-looking lineups against lefties this year, but they're 22nd in the majors against lefties, with a .695 OPS. They're also 22nd in the majors against all pitchers, with a .697 OPS.
Still, it's worth investigating, because if there's a position where the Bucs could easily add a lefty-masher, that might come more cheaply than adding a full-time player. So here are the Pirates against lefties, minimum 30 ABs, again using OPS as a quick-and-dirty measure of performance at the plate.
Starling Marte: 66 AB / 1.087
Jordy Mercer: 38 AB / 1.076
Andrew McCutchen: 60 AB / 1.043
Gaby Sanchez: 60 AB / .961
Russell Martin: 52 AB / .784
Pedro Alvarez: 73 AB / .657
Jose Tabata: 38 AB / .632
Brandon Inge: 35 AB / .457
Neil Walker: 56 AB / .442
Clint Barmes: 38 AB / .411
All the caveats about sample sizes and platoon split regression still apply here. Tabata's numbers against lefties are likely to improve. Barmes' should as well -- he's right-handed, and he had a .712 OPS against lefties from 2010 through 2012. Still, it's worth noting that these numbers aren't that horrible, and Mercer's addition has really helped. I see three potential fixes, only one of which is slam-dunk obvious:
1) Quit letting Brandon Inge hit. The Pirates clearly feel that Inge provides some sort of value we can't see on the field. I guess if you have to play him sometime to cash in on that value, then against a lefty starter is as good a time as any. But Inge appears to be done as a major-league hitter.
2) Find a middle infielder who can hit lefties, and platoon him with Neil Walker. Walker isn't as bad against lefties as his .442 OPS above suggests, but he hasn't been any good against them since 2010, and that probably isn't all statistical noise. Righty Josh Harrison would be a poor platoon partner, since he can't hit, but Ivan De Jesus is right-handed and has quietly had a very good year at Indianapolis. I'm not sure whether it would make sense to promote him and play him at second against lefties; in the long run, the difference between him and Walker would probably be marginal.
3) Platoon someone with Pedro Alvarez. A straight platoon for one of the Pirates' best hitters doesn't really make sense, but maybe Russ Canzler can take some at bats against lefties away from Alvarez when rosters expand.
Other than that, what can you do? The Pirates are set at five positions against lefties, since Marte, Mercer, McCutchen, Sanchez and Martin have all hit well. That leaves only right field, where Tabata should improve, and then platoon fixes for Walker and Alvarez, both of which would be of questionable value. The best solution to the Pirates' issues against lefties is simply to quit playing Brandon Inge ever, at any point. That's something that doesn't take a trade to address. So it's likely that, at the trading deadline, improving against lefties probably won't play a huge role in the Pirates' approach.