How much do Keppinger and Flowers have to produce to replace their forebearers?

This isn’t perfect.

To calculate how much A.J. Pierzynski and the White Sox 3rd base menage-a-trois of pain produced offensively throughout 2012, we can’t just add up the runs, nor the RBI. That is dependent on other players, and an uneven distribution of valuable opportunities. This is why  we rely on rate stats like on-base percentage, or slugging percentage, or weighted on-base average (wOBA).

But that doesn’t allow for us to add production together. We can’t just add wOBA rates of players with different numbers of plate appearances, any more than you can add batting averages together. To express offensive production in lump sums, it’s necessary to convert wOBA in weighted runs created.

The flaw in my methodology–or the biggest one–is that I don’t have a wOBA calculator weighted for the 2012 season readily available. The one Bill Baer loaded up on Crashburn Alley has the weights as detailed initially by The Book by Tango Tiger and Mitchell Lichtman, which are outdated., and will tend to inflate the offensive numbers.

That’s fine, though. These are not projections. Honestly, it’s just an excercise to give a rough idea of a concept.

Last season’s A.J. Pierzynski led the White Sox to outstanding offensive production from the catcher position, whereas Brent Morel and Orlando Hudson were so awful that even Kevin Youkilis couldn’t save the third base unit from being the worst in the league. The theory I was testing is that while Flowers should be a big step down from Pierzynski’s offensive production, Keppinger will be such a step up by not being awful, that the two moves might come pretty close to canceling each other out.

In sum, Pierzynski produced 74 weighted runs created, while the White Sox produced 89 total from the catcher position. Meanwhile, Kevin Youkilis produced 46 in a little over half of a season, and the Sox third basemen still only finished with 56. Let’s express that as wRC+, because it will show how well the Sox hit from this position in terms of league average, with 100 being perfectly average. White Sox catchers rate out as 121 (which is too high, and clues us in to how the numbers are skewed), and third basemen rate out as 71, when 100 even is perfectly average.

Averaging that out between two equal hitters over those plate appearances would require each hitter to hit for a 95 wRC+. That’s a little worse than league average for the both of them–about where Tyler Flowers hovered last season (90 wRC+), and where Jeff Keppinger‘s career average is (97 wRC+), after his excellent season in 2012.

But Keppinger and Flowers, especially Keppinger, can’t be expected to fill in all 600+ plate appearances for their positions, so let’s put them both as 500 each. That leaves 329 plate appearances that wouldn’t be counted for according to last year’s contribution. The Whits Sox bench is bad, very bad, so let’s assume that the backup catcher and middle infielder hit every bit as bad as  the Sox third base group did last season—71 wRC+.

Factoring that into the ineptitude, Keppinger and Flowers burden would be to finish at an average of 103 wRC+.  That’s still only slightly above-average, and within reach if Keppinger can repeat his .big 2012 of hitting 325/.367/.439 for a 128 wRC+, but it gets into the area of asking too much.

Keppinger has never played past his platoon issues and been a full-time success before, and Flowers can offer no guarantees that he’ll keep his strikeout rate in check. Expecting Hector Gimenez, Brent Morel, or Angel Sanchez to contribute professional at-bats off of the bench and make my projections for them look silly, is even more of asking players to do thing they have never done.

So, as reviewed yesterday, accounting for the A.J. departure will probably need a lot of help, and won’t even yet pick at the harsher fact that the White Sox offense wasn’t even that good at year ago.

Follow James Fegan on Twitter @JRFegan