The OP posted by dtoddwin the other day got me thinking about September numbers.  How much different from the rest of the season are they?  Can we treat them like other number sets, or do we have to adjust them?  This is not an exhaustive study, just something to scratch the surface.  If there is interest, maybe I can look into this a little deeper, but I think that what I found is at least interesting.  I realize that his comes with small sample size issues.

My first thought was to look at the monthly OPS numbers for Pujols.  I figured, if anyone can take advantage of AAAA pitching, it would have to be Pujols.   Over the past 3 years, his OPS has actually dipped in the last month of the season, with August showing the largest spike and July showing the biggest drops.

via wozman24.fileave.com

It looks like, if there is a September boost, Pujols is not a beneficiary.  Maybe, to him, all pitchers are AAAA, so there is not much of a difference.  So, what about hitters that profile generally like Pedro.  I took corner infielders with high K tendencies who have most of their value from power, not average.  I also wanted to keep it in the NL.  I came up with 5 names: Ryan Howard, Prince Fielder, Marc Reynolds, Aramis Ramirez, and Adam LaRoche.  I include LaRoche especially because of his reputation for early season struggles and late season success.  If anyone would feast on the lesser competition of September call-ups, I figured it would be LaRoche. 

So what is the average change of OPS from the season average for these three?

Again, not conclusive.  Reynolds does worse, and everyone else gets slightly better, but nothing siginificant.  Definitely not the difference I expected from September call-up. 

There is one more thing I thougth to check.  Last year, Pedro was a mid-year call up.  What about the Septembers of some similar guys who were called up mid-year?  Again I drew from the above criteria of corner infield and National League.  Howard and LaRoche were both called up mid year.  Fielder, Reynolds and Rameriz were not.  I added GFJ to the mix.  We are all familiar with his late season heriocs in his rookie year. 

via wozman24.fileave.com

This looks more like what we expected.  I don't know if there is something really here or not.  It looks like some rookies do better in that last month.  Maybe they are seeing some pitchers that they saw in AAA, so there is some familiarity.  Maybe it is nothing.   More work to be done on this.  I hope this adds to the debate. 

Go Bucs.