Eric Stults should abandon his curveball

Eric Stults is a 34-year-old average starting pitcher who is in his last year of arbitration before being eligible to hit free agency. While the market for him might be shallow now, a simple change in his pitching repertoire could open up some doors.

Eric Stults has a vast repertoire of pitches. According to Brooks Baseball, he throws a four-seam fastball, a changeup, a slider and a curveball, while very rarely mixing in a sinker and a slow curve. Even for a starting pitcher, that's a lot of pitches.

But that doesn't mean they're all worth throwing, and this piece is about a pitch he shouldn't be using, hence the title.

Stults' curveball is terrible. There's no other way to say it, really. Of the 77 qualified pitchers identified by FanGraphs as those who throw curveballs, Stults' curve has been worth the fewest number of runs in 2014 -- -12.7. It wasn't as bad in 2013, but it was still only worth -7.8 runs, which is obviously still dreadful. His curveball is Randy Wolf-esque and averages 67.8 mph; only Henderson Alvarez throws a slower curve.

Stults talked to Corey Brock of MLB.com about his curveball before the commencement of the 2013 season.

"I always had a fastball, changeup and slider, but the curveball wasn't a pitch I started throwing until the last couple of years. But now, being able to mix in a fourth pitch for strikes has helped me and kept me going."

He didn't start relying heavily on his curveball until the 2012 season, and hasn't really shied away from it yet despite it getting worse every year. I would argue that, contrary to what Stults said, his curveball is actually holding him back.

Let's look at some charts.

Hitters have feasted on Stults' curveball during the last two years. A .415 isolated slugging is just nonsense. Stults cut back on his curveball usage a bit this season compared to 2013, but part of that can be explained by the fact he threw 27 fewer innings.

Now, let's look at his vertical release point when he throws a curveball and see if we find anything telling.

Stults' vertical release point dropped two inches in 2014 after staying relatively steady the past two years. This is unusual. A curveball usually requires a higher release point in order to get the type of break it requires. This could explain Stults' curveball struggles.

He doesn't need a curveball to have success. His changeup, which was his best pitch this season (4.5 wCH) and most used behind his fastball, does a nice job taking pressure off his low velocity fastball, and his slider has been worth positive runs throughout his career. Adding a pitch, such as the curveball, just to expand the number of pitches in an arsenal is fruitless, especially when it's not even an effective pitch. And that's essentially what Stults did.

If Stults wants to continue throwing the curveball, he needs to mix it in a lot more sparingly. He definitely doesn't need it to remain a mediocre pitcher, which he's been his entire career. But he can be less mediocre if he forgets about his curveball.

. . .

All statistics courtesy of FanGraphs and Brooks Baseball.

Justin Schultz is a Featured Writer at Beyond the Box Score. You can follow him on Twitter at @JSchu23.