The next step of Wily Peralta's development

The 2015 Brewers are set up to be pretty average. That's not a good thing but it's not a bad thing. But there are spots where the Brewers can eke out some upside-- basically it's a list of things that would have to go right to contend this year. Every middle of the pack team has one of these. It consists of things like Braun returning to form, none of the veteran starting pitchers not falling off, and so on.

But the area where the most actual upside might exist is in the bottom end of the starting rotation, and particularly in Wily Peralta. Peralta projects out as an average to slightly above-average starter this season. That has a good amount of value, and means that he has worked out as a pitching prospect; he's a real success story for the Brewer player development system. But with his arm, stuff, and durability, you can't help but hope for more. And I have a feeling that at the end of the 2015 season, we may look back and say that the difference between beating expectations or falling short on the aggregate may come down to Wily Peralta.

Right now the book on the Brewers rotation (not to mention the team more generally) is that they're average across the board. The Brewer rotation last year was average in a different way than most average rotations are average, in that it contained (and projects to contain) 5-6 starters who project to be worth about 2 wins better than a replacement-level starter over the course of a year. Most teams have a more even distribution between good and bad, whereas the Brewer 5th starter isn't very much different  If Peralta can develop into a front-line #1 type starter, the rotation starts to look a lot different.

Let's take a deeper look at how Wily might be able to do it.

What Peralta does well

Wily starts out with the huge advantage of having an arm capable of throwing a baseball 98 or 99 miles per hour. He uses that top-end velocity to generate a fantastic rate of ground balls allowed. Among qualified starting pitchers he was 11th in the majors in ground ball rate last year, and that's nothing out of the ordinary for him. This shouldn't come as a surprise; his best pitch is a power sinker that's thrown 1.8 standard deviations harder than an average sinker and comes in with .6 standard deviations more vertical movement than the average sinker that batters see.

Peralta had his best year in 2014 because he drastically cut his walk rate and drew a ton of groundballs. His strikeout rate was fine but not spectacular. He was a solidly average starting pitcher.

What Peralta could do better

This is where it gets a bit counter-intuitive-- to take the leap from above-average starter to All-Star caliber frontline starter, Wily probably has to reinvent himself a bit. That probably involves switching up his game to the detriment of his best skill.

Inducing groundballs are a great outcome for a pitcher, but they're an outcome that in an ideal scenario are the byproduct of a good process, not the end goal. Most great pitchers have high strikeout rates and high swinging strike rates, and also tend to induce a high amount of ground balls as a byproduct by keeping batters off balance and making weak contact with awkward swings.

Just take a look at the ground ball leaderboard among starting pitchers from last year. It's not quite like browsing the strikeout leaderboard, which often doubles as a List of Great Pitchers. All the main horses are on the groundball leaderboard-- Hernandez, Kershaw, Kluber, Greinke, and so on. But there are also a lot of average-ish pitchers with much lower K rates, including our own Peralta and Yovani Gallardo. Again, average isn't bad, but if Wily could take a step forward and use his stuff to accumulate some more strikeouts, even at the expense of some groundballs, there's a possibility that he can make the jump to elite level.

How Peralta can do it

I'm not a scout and I don't think there is an incredibly obvious suggestion for Peralta like I have sometime seen when looking at data. But here are a few ideas:

Embrace the high fastball. The high fastball has experienced something of a resurgence in the past year or 2 as part of the backlash against pitchers pounding down in the zone over and over more than ever. Wily's strikeout pitch against both righties and lefties is a slider down and away to a righthander and down and in to a lefty. Check out his location frequency heat map in all 2 strike counts:

It's a very effective pitch but it's also not tough to see coming. The problem has been that Wily hasn't developed a great third offering to keep the opposition honest. His changeup is in play about 10% of the time against lefties but barely existent against righties. If he's not confident in using the change very often, Wily could take a page from his teammate Mike Fiers and utilize the high straight fastball out of the zone as a second strikeout pitch, instead of just as a pitch he uses to get back in the count when he's behind.

Try something new against lefthanders. In his career Wily has a higher strikeout rate against lefthanded batters than righthanders, but has had worse outcomes-- a .343 wOBA to lefties vs. .291 to righties on the strength of 59% groundballs vs righties and just 46% against lefties. But it's not the case that he works higher in the zone to lefties, it just seems to be the case that his offerings are less effective in inducing groundballs. Instead of doubling down on what seems to be a losing strategy of working down in the zone and attempting to mix in the changeup against lefties, he could work the strikeout angle harder by working in different areas of the zone instead of constantly trying to pound the lower third.

Mix up something with the change-up. Like many pitchers before him, Peralta was pressed throughout his development in the minors to use his changeup often to develop it. Eventually, his fastball/sinker/slider combo was good enough for him to get out batters in the majors, but his change hadn't developed to the point of being deployed effectively against major leaguers. He needs it now to take the next step, but he lacks the command to use it regularly and it shows-- it's his worst pitch in terms of at-bat outcomes despite a healthy enough 13.5% whiff rate. Now he's caught in no-man's land with the pitch and should re-commit to using it more often starting in spring training or nearly ditch it entirely and work on something else.

Wily Peralta isn't broken. Without altering his approach at all there's a great chance he gets even better than he was last year. But if he could be a little less Roberto Hernandez (49.7% ground balls in 2014, 5.74 K/9) and a little more Felix Hernandez (56.2% ground balls, 9.46 K/9), the Brewers are going to contend this year.

(Standard credits to Brooks Baseball Pitch F/X database and Fangraphs for making it so easy to access all the great MLB gameday data)