As chuckb so elegantly put in a post yesterday over at Viva El Birdos, Kyle Lohse has been pitching like a giant pile of Todd Wellemeyer since coming back from injury. To help illustrate this, I present to you an informative table:

You can see that everything is trending in the wrong direction.  He's pitched fewer innings, walked more, struck out fewer batters, and has allowed more balls to leave the yard.  That's manifested itself in a ridiculous 7.79 FIP in 5 starts since returning from injury.

So why is he pitching so poorly?  Besides the obvious answers shown in the above chart, I wanted to take a closer look.  First let's check out his stuff before and after the injury, graphed by vertical and horizontal movement:

The first thing you can see is that his changeup velocity has seemingly risen, while his fastball velocity has seemingly decreased.  That is not actually the case.  He has been throwing a lot more 85-86 MPH pitches, that I had trouble classifying them.   This actually means the his mean fastball velocity is probably significantly slower than shows above.

While before the injury he had two distinct groupings, an 80-83 MPH changeup and an 88-92 MPH fastballl, that distinction is gone and now his fastball and changeup are getting harder to tell apart.  You can also see that the movement on those pitches has become more concentrated as well, further blending the two pitches.  These aren't good signs.

His breaking pitches look fine at least.

Now let's take a look at his location.  For this I split the strikezone into 9 different zones, and measured the percentage of pitches thrown in each zone:

This may be a little fuzzy, but you can click on it for a larger view. 

Remember, these are the percentages out of all pitches, not just strikes.  The blue dots are, of course, the pitches thrown out of the strike zone.  Also, this is from the catchers point of view.  Bearing those things in mind, here are some observations:

1)  He's elevated more pitches in the strike zone.  Before the injury, 10.8% of his pitches were in the upper third of the strike zone, and after, 13.7% were in that area.  That may not sound like a lot; however, over the 445 pitches he has thrown after the injury, that difference equates to about 14 pitches.  As Jonathon Hale pointed out, pitches higher in the strike zone get hit out more often.  The fact that Lohse is elevating the ball more, and throwing his fastball with less velocity, is likely the reason for his elevated HR rate after the injury.   

2)  He has only been hitting the strike zone slightly less often.  The box shown above is perfect, but it's a pretty good approximation of the major league strike zone.  Before the injury, threw 54.4% of his pitches in the strike zone, and after, he's thrown 53.7% in the zone.  That equates to about 3 fewer strikes, which isn't significant.  That doesn't explain the 1.5 BB/9 raise in his walk rate.  It seems that he's either getting squeezed more, or is not getting hitters to chase at pitches outside of the strike zone as often.

We can test both theories pretty easily, based on the outcomes of each pitch:

Of course, it's pretty hard to draw conclusions from this, so let's check out some stats:

"Squeeze%" and "Gift%" are my own two little made up stats, that measure the percentage of pitches in the strike zone called balls, and the percentage of pitches outside the strike zone called strikes.  As you can see, he has been getting squeezed more often (to the tune of about 10 pitches) and has been getting fewer gifts (to the tune of about 10 pitches).  So all in all, he could easily have 20 more strikes called.  Given that strike% has a direct relationship to walk%, that's a big factor in why his walk rate his gone up so much.  

However, that doesn't explain of all it.  As I hypothesized, batters have swung at fewer pitches outside of the strike zone.  O-Swing% has a very strong correlation to walk%, as I showed here.  The difference in O-Swing% is about 8 pitches.  If you combine that + the "squeeze" fact + the fact that he has been throwing fewer pitches in the strike zone, we would expect him to have thrown about 30 fewer strikes after his injury.  In 445 pitches, that equates to a difference of about 7% more balls.  If you go to Statcorners' leaderboards, and sort by Ball%, you'll see that 7% is the difference between guys like Roy Halladay and guys like Jason Marquis.  The difference in BB/9 between those two... 1.53, which is identical to the difference between the post and pre injured Kyle Lohse.

So what if you take out the bad calls by the umpire?  Well, than Lohse expected strike% difference goes down to 2.5%.  You would then expect his walks to raise by about .5 per 9 innings, which would only be about 3 BB/9.  That's not nearly as bad as his 4 walk pace after the injury.  

Another thing to notice about the above chart is that batters are making way more contact on his pitches.  His swinging strike rate has dropped to Livan Hernandez levels, and he's allowing a lot more contact on all of his pitches.  Given that contact% has about a .80 correlation to strikeouts (based off of 06-08 data), that almost completely explains his plummeting strikeout rate.

Conclusion

After the injury, Lohse has lost velocity on his fastball, and has suffered a diminished distinction between his fastball and his changeup because of it.  He has also been locating balls more up in the zone, and throwing slightly fewer pitches inside the strike zone.  Those two factors, combined with some help from the umpires, has lead to more contact by opposing hitters, more HR's, more walks, and fewer strikes.  Those are directly responsible for his skyrocketing FIP.

Basically, he's been worse in every area of pitching.  Yes he's been getting hurt by bad umpiring; however, even if you adjust for that, he still looks terrible.  Whether this is due to injury or early decline (I really hope it's the former), he clearly shouldn't be allowed to pitch right now.