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What's the deal with splitters, anyway?

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A look at the history and concerns over the split-finger fastball and whether or not we should apply those concerns to Junior Guerra. Also, look who has arguably the best splitter in baseball!

Koji throwing a split-finger fastball.
Koji throwing a split-finger fastball.
Kevin Sousa-USA TODAY Sports

The split-finger fastball and the MLB have had a messy breakup.

They say the splitter was in vogue during the 1980's (I wasn't around for the 80's, nor is there any PITCHf/x data available from that time period to sort through, so I have to go entirely off of hearsay).  Almost every pitcher threw one, as they recognized its innate ability to create swings-and-misses. And then MLB pitching coaches began to start telling the pitch, "It's not you, it's me." But that was a dirty lie, as it was the nature of the pitch's effect on arms that began to scare away entire organizations. It was really just the pitch.

So what is it about this pitch that is so frightening? If you are reading this, I'd like you to extend your index and middle fingers on your throwing hand and spread them as wide as you can. Now keep alternating between close together (fastball grip) and far apart (splitter grip). You might have noticed, though I'm not sure if everyone feels this, as your fingers are spread farther apart, there should be a little more stress in your elbow region. Or, if you have a baseball handy, shove it between your fingers like Koji Uehara is doing in the picture at the top. I'm guessing that's not great for you either.

It is hard to narrow down pitcher injuries to a singular pitch, and there are many variables that go along with every pitcher and injury. But it's that strain on the elbow which has led many in the industry to preach against its use. It's a devastating strikeout pitch, but for most, the long-term health outweighs the short-term rewards.

And that has led to 2016, a season in which there are only eleven starting pitchers using their split-finger fastballs over 10% of the time. Of course, the only reason any of us have splitters on the brain is because one of the pitchers high up on that list throws for the Brewers.

In the table below, I have included the five highest usage split-finger fastball starting pitchers of 2016 along with their usage of the pitch, the amount of whiffs per pitch, batting average against, slugging percentage against, and isolated power against. I'll give you a moment to take a gander.

USG% WHIFF% BAA SLG ISO

Matt Shoemaker

33.0% 22.22% .194 .280 .086

Masahiro Tanaka

30.3% 17.27% .174 .261 .087

Junior Guerra

26.3% 20.71% .143 .245 .102

Alfredo Simon

22.4% 10.58% .365 .539 .173

Hisashi Iwakuma

20.7% 18.14% .236 .375 .139

Junior Guerra is, by most measures, up there as one of the premier split-finger fastballers in all of baseball. The short-term reward is easy to see, as he's drummed up a great deal of excitement every fifth game along with outstanding results. To be sure, he has blown by the expectations for your average 30-year-old October waiver claim.

However, along with those short-term rewards is the long-term question of elbow health. Though with Guerra, that question carries a different sort of vibe as he is a 31-year-old rookie as opposed to a 21-year-old one. Another thing to consider with regards to Juni G's health is his workload increases. In 2014, he threw 78.0 innings in the Venezuelan Winter League. Last year, Guerra tossed 87.1 innings in the regular season, with an additional 56.2 IP in the VWL. This year he's currently sitting at 65.2 IP between AAA and MLB. At his current rate, he will have thrown approximately 173 innings by seasons end, a 97.3% increase over last regular season.

But what is long-term in this scenario? I'm not sure anyone knows what will happen moving forward. Will he start the rest of the season? Will he be with the club next year or will he regress dramatically? How long is he in the club's plans? I'm not sure anyone knows the answers to these questions.

If pitching coaches throughout the MLB are correct, Guerra may have some elbow troubles in his future. However, this is far from the rule. Look at the guy at the top of that list above. Matt Shoemaker has been near the league lead in split-finger fastball percentage for the past three years, and according to this site, has yet to spend time on the DL. There are so many variables involved, it is possible that Junior simply will remain healthy while throwing the controversial pitch. Only time will tell. In the meantime, we can sit and enjoy watching the beauty of #2016ThirdHighestSplitterUsageSP / #2016BrewersAce.

Statistics courtesy of FanGraphs and Brooks Baseball.