Edinson Volquez, probably in an attempt to revitalize his career, started throwing his sinker more than his fastball in 2013. Er, I would say revitalize his career except that's not really the case. It just seems to be the case with many other pitchers. A.J. Burnett comes to mind. Burnett was having a terrible time in New York, but he went to the Pirates and starting throwing tons of sinkers in front of an often-shifted defense. That worked well.
Volquez, on the other hand, was coming off a 1.5 fWAR season with the Padres in 2012. His velocity had not declined in 2012. The horizontal and vertical movement on his pitches hadn't materially changed in 2012. I'm not really sure what led to the change in 2013, but Volquez greatly increased his sinker usage that year. The only thing that seemed to change in 2013 with his sinker was the velocity; it declined. In terms of results, I don't like what's happening.
I realize there's a lot of white space in that graph, and it looks ugly and gross, but I didn't want to manipulate the axes so much that everyone thinks the decline is more than it is. It's modest, but it's important. OPS allowed up. Whiffs down. Yea, sinkers aren't designed to get whiffs, but I chose those two measures to show the decline in usefulness of the pitch. Volquez's ground ball generation has not made up for the declining whiffs; his GB% has fluctuated around 50%, which is somewhere around average for sinkers, perhaps even a little below average.
Volquez's bread-and-butter pitch has been neither bread nor butter. Volquez actually walked more guys than struck out in 2014 when the plate appearance ended with the sinker. You and I and probably several other people would think a 95mph sinker would be an OK pitch. I think it would be if Volquez could control where it went.
Vs. RHH, 2014
Vs. LHH, 2014
A sinker doesn't really have any business being located up so high. Looking at those zone profiles, there doesn't really appear to be any location tendency. I would say it gets left in meaty parts of the zone too much, and it gets crushed when it's there. Volquez has to do something about this.
Maybe he is. I was watching his final exhibition start on Friday against the Astros. From a short viewing, it looked like Volquez showed some decent command with his sinker. It looked like he was doing a good job of painting the corners. I went to Baseball Savant for the data. Here is the heat map of his PitchF/X sinker, which may be slightly different than Brooks Baseball's sinker. Should be pretty close.
Volquez did an OK job of staying out the middle of the zone. There are some low and away pitches and some inside corner pitches (if all hitters were right handed). It's still a bit scattered, but if Volquez can paint the corners with his sinker, that will go a long way toward better results.