Luke Hochevar's production has baffled me for a while. Rany just the other day noticed that Luke's production is much worse with people on base. Previously, I noticed that Luke loses steam as the game goes on.
After much research, we were both right. I will try to keep the explanation as simple as I can.
Here is a graph of Luke's fastball speed (2008 to 2011) by inning when there was a base runner or when there wasn't one on base.
Luke loses about ~1 MPH from the 1st to the 7th innings. Also, he loses ~0.33 MPH when he pitches from the stretch. Mike Fast has looked into the average increase in Runs Allowed per 9 innings to be -0.26 for every MPH decrease in speed. So in Luke should expect and increase of R/9 of about 1/3 of run. This change doesn't explain all of Luke's drop off, does explain some.
Luke gets hit with two blows against him as a game goes on. First his fastball slows down and becomes easier to hit. Once hitters begin to get on base, Luke has to pitch from the stretch. While pitching from the stretch, his velocity decreases even more making his pitches even easier to hit. This double blow was evident last Wednesday when he took a perfect game into the 6th inning and then the wheels just came off for him after the first hit.
Thanks to David Allen and his side burns for helping for helping with the data.