What's Wrong with Liriano?

Francisco Liriano (MIN) turned in a stellar 2010 season, but through five starts in 2011 his ERA stands at 9.13.  His control is poor and he allowed nearly half his 2010 home run total.  The most glaring difference between 2010 and 2011 for Liriano is a drop of velocity on his fastball:

Francisco Liriano, fastball graph, 2010-2011.His velocity dropped about 1.5 MPH from 2010, down to 92 MPH on average.  While batters made contact with his fastball often last season, that is up too as the slower pitch is easier to hit.  Despite the drop, his opposition batting average isn't that much worse, it's the power and walks that are getting to him:

Vs. Fastballs	2010	2011
Batting average	.323	.320
OBP	.388	.435
Slugging average	.462	.520
wOBA	.369	.415

There is a secondary effect as well.  Liriano's change up stayed at about 85 MPH, meaning it looks less different than his fastball this season.  The opposition can hit that pitch better as well.

Vs. Change Ups	2010	2011
Batting average	.241	.294
OBP	.252	.333
Slugging average	.340	.588
wOBA	.256	.385

The change was a great out pitch for Francisco, and now batters are waiting to power it out of the park.