Johan Santana is disappointing some people this year, but if we take a moment to look at how he's really doing -- use whatever you want: ERA+, WSP, RA, FIP -- we can see that he's actually pitching better than he did last year. If the Mets expected Santana vintage 2007, they should be happy with their returns so far.

However, as good as Santana's performance has been in 2007 and 2008, it's not nearly as good as it was from 2004 to 2006. I checked out his pitch data on BJOL and found one thing that really popped out: he's not throwing sliders to righties as much as he used to.

Sliders to righties:

2008  7% v R
2007  7%
2006 14%
2005 13%
2004 13%

Instead, he has been relying more on fastballs and change-ups. As he has gone away from throwing sliders to righties the past two seasons, righties have hit him much better. Here is his OPS allowed to righties since 2004:

2008 691 v R
2007 688
2006 589
2005 564
2004 562

Rob Neyer recently quoted a scout who said Santana's fastball has lost some life. One reason he could be using the slider less to righties is that it's just not biting the way it used to. If he has lost some bite on his slider and he has had to go with more fastballs, and the fastball has lost some of its life, that would go a long way towards explaining why he has declined from great to merely good.

There is some thought that a slider is hard on the arm and Santana does have some history of arm trouble. It could be that he's favoring that arm a little by putting less torque on it.

However, if that were the case I would expect him to use the slider less against lefties too. That's not what your data shows. As Santana has been pitching differently to righties and doing worse, he has been throwing essentially the same repertoire to lefties and doing better.

Leaving aside the rest of the repertoire against lefties, here is his percentage of sliders over the past few seasons:

2008 25% v L
2007 25%
2006 23%
2005 24%
2004 19%

And his OPS allowed:

2008 698 v L
2007 650 
2006 737
2005 737
2004 575

We have a little more evidence that his problems are limited to righties: His strikeout rate against righties is down 14% (2007-2008 compared to 2004-2006), while his strikeouts against lefties are up 12%.

If he has lost that slider as a good and regular option against righties, he's down to two pitches to use against them: the great change-up and reportedly diminished fastball. His GB% is way up this year, so maybe he's compensating with a cutter or sinker or something we're not seeing in this pitch data yet. Whatever the case, it looks like the slider may be a key to figuring out why he doesn’t quite dominate the way he used to.

Keith  Scherer