The Pirates signed Matt Diaz to be a platoon player. At first, the signing sent me off on a bit of a chicken-or-the-egg train: Can 105-loss teams have the luxury of platoon players? Or would 105-loss teams not be 105-loss teams if they knew how to effectively employ a platoon? That's clearly an unproductive line of thinking, but then I started to wonder about right-handed platoon players. How many right-handed platoon players are there?
The value of a left-handed platoon player is obvious. Garrett Jones, who Diaz will be sharing time with, had 654 PAs in 2010 and 424 of them were against righties. A right-handed platoon player, though, is a pinch-hitter two of every three nights. This may just be my own bias showing, but when I think of platoon players I think of lefties that can't hit lefties at all and not of the righties that tend to replace them a couple nights a week. That leaves me with a couple of questions: First of all, can a player be effective only playing against left-handed pitching? And secondly, how much value is there in that sort of niche role?
That first question isn't all that easy to answer; splits are available but not generally searchable via something like the Play Index. Instead, let's just look at Diaz's career. He's gotten at least 200 plate appearances every year since he joined the Braves in 2006 except one, so let's look at his platoon splits over his Braves' career.
|vs RHP as RHB||87||166||151||54||10||1||2||16||7||26||.358||.400||.477||.877||72||5||2||.416|
|vs LHP as RHB||76||156||146||43||5||3||5||16||4||23||.295||.327||.473||.800||69||4||1||.317|
|vs LH Starter||41||41||161||149||46||4||2||5||16||5||20||.309||.338||.463||.801||69||3||1||.323|
|vs RH Starter||83||21||161||148||51||11||2||2||16||6||29||.345||.391||.486||.878||72||6||2||.415|
|vs RHP as RHB||107||180||170||54||6||0||3||18||6||36||.318||.350||.406||.756||69||3||1||.386|
|vs LHP as RHB||81||204||188||67||15||0||9||27||10||27||.356||.384||.580||.964||109||1||2||.372|
|vs LH Starter||63||63||256||240||85||16||0||9||30||11||40||.354||.384||.533||.918||128||2||2||.394|
|vs RH Starter||72||15||128||118||36||5||0||3||15||5||23||.305||.336||.424||.760||50||2||1||.347|
2008 was the year he didn't play much due to injury, so we'll skip to 2009:
|vs RHP as RHB||100||273||235||60||7||3||7||34||24||70||.255||.349||.400||.749||94||10||2||.335|
|vs LHP as RHB||65||152||136||56||11||1||6||24||11||20||.412||.464||.640||1.103||87||3||0||.450|
|vs LH Starter||48||45||193||172||68||9||3||7||32||13||31||.395||.447||.605||1.052||104||4||0||.452|
|vs RH Starter||77||47||232||199||48||9||1||6||26||22||59||.241||.343||.387||.730||77||9||2||.313|
And finally, his rough 2010:
|vs RHP as RHB||68||114||103||23||5||1||2||16||6||18||.223||.283||.350||.633||36||3||1||.250|
|vs LHP as RHB||53||130||121||33||12||1||5||15||7||26||.273||.318||.512||.830||62||1||2||.311|
|vs LH Starter||41||41||163||148||42||13||1||5||24||11||30||.284||.335||.486||.822||72||1||2||.325|
|vs RH Starter||43||12||81||76||14||4||1||2||7||2||14||.184||.235||.342||.577||26||3||1||.200|
Diaz actually hit righties better than lefties in 2006 and he had a pretty good year in 2007 playing primarily against lefties. He wasn't terrible against righties that year either, but I'd guess that not playing against the tougher righties was a factor in both seasons. He was flat out awful against righties last year, especially as a starter (though the sample size is awfully small).
It's pretty clear that Diaz can hit lefties, even if he's only playing irregularly. Even last year, when he made 41 of his 53 starts against left-handed pitching, he put up a respectable .822 OPS against lefties. The other thing that's apparent, though, is that it's going to be more or less impossible to prevent him from ever facing a right-handed pitcher. I'm sure he'll pinch-hit against righties plenty, but he'll likely get some spot starts on nights when Jones plays first base or is slumping or when Jose Tabata gets an occasional off-day. Over his career, Diaz has hit righties about the same as a starter as he has as a pinch-hitter:
|vs RHP as RHB||418||849||769||207||31||7||14||92||47||185||.269||.327||.382||.710||294||22||6||.336|
|vs RH Starter||320||113||709||642||167||31||6||13||71||39||151||.260||.321||.388||.709||249||21||6||.319|
That's better than Jones's career numbers against lefties (.210/.249/.381), but it's also important to note that Diaz is 33 and his worst year against righties was last year, which is worrisome. I know I'm not hurtling towards any ground-breaking conclusions here, but seeing all the numbers laid out like this does confirm most of what I suspected when Diaz was signed. I'd rather have him playing against lefties than Jones, but there's no reason to trot him out against a righty just to "keep him fresh" or other such nonsense. It's inevitable that he'll get hot and see an extra start here and there, but he shouldn't get much more than that and I doubt he really needs it.