Philadelphia’s A.J. Burnett has issued a league leading 47 walks in 111 innings pitched so far this season and it is evident that he is struggling to get his fastball over the plate.
Burnett’s heater is also losing some of its zip. He hit an average of 92.4 miles per hour in 2013 but has clocked in a full MPH lower in 2014 (91.4).
We see that same velocity drop when we look at his velocity in June of last season (92.5) to June of this year (91.4), and studies have shown that losing velocity in June or July increases a starter’s odds of finishing the year with an overall velocity loss the most.
If a pitcher is down at least 1 mph in June relatively to the previous June we shouldn’t expect them to magically recover their velocity in the second half of the season. Part of this, of course, is timing–you don’t have as many pitches left in the season to recover.
And for Burnett, the loss of velocity is showing up in the results and could plague him for the remainder of the season. For example, the weighted on-base average against his fastball is 0.391, close to his wOBA yielded in 2010 when he went 10-15 with a 5.26 ERA.
For a pitcher like Burnett, who has just two primary pitches — a fastball and curve — it is even more damaging to lose one of the weapons in your arsenal. He throws the fastball 61.4 percent of the time, mixes in a curve on 32 percent of his pitches and fills in the rest with a change-up, but his fastball is the least effective it has been since 2011.
The updated ZiPS projections have Burnett finishing the season with a 10-13 record and 3.98 ERA in more than 200 innings, but with the way his fastball is performing I think even that may be optimistic.