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Wily Peralta might be a changeup away from breaking out

Is he a mid-rotation starter? Can he be more? Should we expect less? Let's take an in-depth look at what Wily has given us to this point, and what we can reasonably expect going forward.

Wily Peralta does some soul searching.
Wily Peralta does some soul searching.
Benny Sieu-USA TODAY Sports

Way back when I was graduating from High School, Yovani Gallardo was frequently talked about as a potential Cy Young Award winner. It became trendy to predict Yo as a breakout candidate every off-season. Sadly, we were left waiting. After his rookie season and injury-shortened sophomore campaign, Gallardo submitted six solid, steady seasons for a team starving for a home grown ace. And then he was gone. And then the dreams were shoved onto Wily Peralta.

Wily Peralta is a quality righthanded starter. Power fastball, improved changeup: He's the one guy on the staff who could start for anybody, with Matt Garza hurt so much.

That was an anonymous scout's take on the Brewer's Opening Day starter for a Sports Illustrated article recently. Perhaps you've seen other predictions and opinions like it. The thing I'm wondering is if that is an accurate assessment. Could he start for anyone? Should we continue hoping Peralta takes a leap forward, or should we resign ourselves to accepting him for what he is? What is he anyway?

Let's start by breaking down Wily's pitches. According to Brooks Baseball, Peralta has four pitches. Those are Sinker, Slider, Changeup, Fastball. I should put sarcasm quotes around "four pitches," because he mostly throws the Sinker and Slider. For instance, on Opening Day, Wily threw two fastballs and eight changeups on 83 pitches. Compare that to the 22 sliders and 51 sinkers he threw, and you see that his fastball and changeup are more ideas than actual pitches. But let's take a closer look at his top three pitches (All pitch data is taken from Brooks Baseball):


This is Peralta's bae, his bread and butter. That fact is understandable for a number of reasons. First of all, it's his only pitch that consistently induces ground balls at about a 50% rate. Here are his groundball percentages for every season since his rookie campaign: 70%, 49.63%, 53.49 %, 50.89%, and (from opening day) 50%. Every other pitch in his repertoire is fly-ball prone, a trend troubling especially at Miller Park.

The general problem with splitters is that they tend to be contacted more often than not, so high strikeout totals should not be expected. Wily's splitter is no exception, and it's swing-and-miss rate has plummeted in the past four years:

While his most used pitch is effective at creating easy outs for the infield, it has not been very effective at striking guys out. Thankfully, that's why he throws a slider.


This is Wily's second most used pitch and the best at inducing whiffs. In his first three years, the groundball% for his slider was around 50%, but last year it dropped to a low 40.28%. So while not quite as good at creating easy outs as the splitter, it created many more swings-and-misses at season rates of: 19.05%, 15.19%, 15.17%, 10.99% and 18.18%. That's not elite level, but it should be his go to pitch when trying to earn a K.

The problem with Wily's slider, as most sliders, is the fact that it does not work well against opposite handed hitters. While an effective pitch against lefties in his first two seasons with an ISO against of .071 and .135 respectively, in the last two years, those ISOs jumped to an above average .161 and a superstar level .259. This displays the importance of a changeup, a generally effective pitch to use against opposite handed batters.


The problem with Wily's changeup is that, statistically speaking, it's not very good. Fiddle around with this chart, and you'll soon find out that vRHH or vLHH, Wily's been all across the board in terms of changeup effectiveness. While a decent strikeout pitch against LHHs with whiff rates of 14.06% and 14.47% over the last two seasons, it is still much more flyball and linedrive prone than either his slider or splitter.

In 2013 and 2014, Peralta threw 195 and 157 changeups, respectively. In those years, opponents slugged .633 and .727 against those changeups. In 2013, it was RHHs that crushed his changeup, in 2014 it was LHHs that crushed his changeup. It's clear that he has experimented with his changeup through the past four years, but he has received very mixed, and even discouraging, results. Thankfully, Wily has continued to use his changeup around 5% of the time, so clearly he has not given up on it.

So what is he?

Peralta reminds me of the old guy from Monty Python saying, "I'm not dead yet!" It's true, he's not dead yet. He's only 27 years old this year. He still has several years to contribute before he reaches the typical decline years.

Up to this point, he has been effective against RHHs with a triple slash of .253/.324/.351 and less effective against LHHs with a triple slash of .289/.348/.458. If he's truly going to break out this year or any time, he will need to improve his changeup so that his platoon splits become less pronounced. Thankfully, he's still relatively young, he seems to know he needs to keep working on his changeup, and he has a pitching coach who's most likely working with him on his repertoire and pitch selection.

Could he start for any team in the league? I don't know, you can decide that for yourself. I think it would be accurate to say any team in the league would be happy to have him. He's a big-bodied, right-handed sinkerballer who can suppress flyballs and has the capability to hit 200 innings. That is valuable, and if he learns an effective changeup, he could be more than that. Hopefully he figures it out soon as we busily try to figure him out as well.