August 21, 2015

Ducks on the Pond

David Peralta: Tony La Russa's Savior

by Chris Mosch

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Back in November, Diamondbacks Chief Baseball Officer Tony La Russa was quoted saying that he would "be absolutely brokenhearted if we don't have a winning record next year," a comment that drew its share of snickers from the Internet. The idea behind La Russa's quote was that the organization didn't plan on a full-bore rebuild and that he wanted to prove to its fan base that they could be competitive in the immediate future. However, the outlook was bleak for a team coming off a 98-loss season in 2014, one that PECOTA projected for 73 wins. Only the Phillies were pegged to finish with a worse record in the National League.

Fast-forward to today, with just over a week to go in August, and La Russa's heart might make it to the end of the season in one piece. The Diamondbacks aren't going to make the playoffs, but they're hovering around .500 and their third-order winning percentage indicates that, if anything, they've been slightly unlucky. Moreover, a handful of promising young players have emerged on which the club can build around going forward.

Nearly all of Arizona's success this season can be attributed to position players. The offense ranks fourth in baseball in True Average and defensive metrics are enamored with the team's glove work: Arizona is neck-and-neck with Kansas City for the most Defensive Runs Saved and ranks fourth by Ultimate Zone Rating. (Raw defensive efficiency and PADE put them a bit above average.) But aside from Robbie Ray, the starting rotation has been a mess, ranking at the bottom of baseball in both DRA and cFIP, while the bullpen has been middle-of-the-pack.

The offensive attack starts exactly where you think it does: Paul Goldschmidt and his incredible .353 True Average; combine that with Gold Glove–caliber defense and a bit of value added on the basepaths and you've got a seven-WARP player, with more to come over the final month. A.J. Pollock has come into his own this year as an excellent second weapon, sporting a .302 TAv paired with stellar defense in center field.

One performance that has flown under the radar, however, has been the breakout of David Peralta. One of the coolest stories last year was how Peralta went from being a failed minor-league pitcher to independent-league outfielder to productive major-league outfielder in the span of five years. Just being an above-average hitter in his rookie season validated Peralta as one of the best scouting successes in recent memory, but he has become more than just a feel-good story in 2015. Through Wednesday's games, the 28-year-old boasted a .319 True Average, sandwiching him between Adrian Gonzalez and Mark Teixeira for the 12th-highest mark among qualified hitters.

What has accounted for a nearly 50-point uptick in TAv for Peralta during his sophomore campaign? Let's take a cursory scan at what has gone better for him in 2015.

	BB%	K%	ISO	BABIP
Peralta 2014	4.6%	17.2%	.164	.328
Peralta 2015	9.1%	20.6%	.218	.354
MLB 2014-15	7.7%	19.8%	.143	.300

The first thing that sticks out is the more patient approach at the plate, where he's worked deeper counts and thus doubled his walk rate at the expense of taking a few more called third strikes.

	Zone%	Swing%	Contact%	Z-Swing%	O-Swing%	Z-Contact%	O-Contact%
2014	44.5%	49.1%	79.2%	63.5%	37.6%	89.3%	65.5%
2015	43.7%	45.8%	78.1%	65.6%	30.2%	89.0%	59.7%

Peralta is seeing a little more than 0.25 more pitches per plate appearance this season, the 14th-largest increase among hitters with at least 250 plate appearances each of the last two seasons. Nearly all of that can be attributed to him watching more pitches out of the zone go by, as he hasn't sacrificed much in the way of contact. His chase rate has dropped by over seven percentage points while he's actually been slightly more aggressive against pitches inside the strike zone. If you prefer visuals, here are a couple of heat maps illustrating how the left-hander has tightened up his strike-zone recognition.

In particular, Peralta is spitting on more breaking balls and off-speed stuff below the knees this year along with taking more balls off the outer part of the plate. Not only is Peralta laying off more pitches just a bit outside, but when he is getting pitches to hit on the outer part of the plate, he's doing more damage with them. In an interview last week, Diamondbacks skipper Chip Hale credited Peralta for "starting to figure out when to shorten his swing and use the other side of the field." The results speak for themselves. Over at Baseball Savant you can break up different areas inside and outside of the strike zone as follows (catcher's POV):

Peralta's Isolated Power on pitches away (Zones 1,4,7,11, and 13) this season has increased from .123 in 2014 to .213 in 2015, a power spike that can be attributed to him using the opposite field more often. Let's take a look at what Peralta has done with pitches away in each of his first two seasons.

Last season, when Peralta got pitched away, it was common for him to roll the ball over to the right side of the infield, but, as Hale noted, Peralta has figured out when to use the opposite field this season. You can see that he's been driving the ball the other way more often:

	Oppo% on pitches away	Pulled GB% on pitches away
2014	39%	43%
2015	49%	33%

Despite the strides Peralta has made at the plate, he still exhibits a noticeable platoon split, which limited him to a part-time role during April and May. Peralta played winter ball in Venezuela last offseason to get more reps against same-side pitching but it wasn't until Ender Inciarte went down with a hamstring strain that he got regular playing time against lefties. A month of playing time isn't enough to draw any statistical conclusions about whether Peralta has gotten any better against lefties, but he impressed Arizona enough to retain consistent playing time even after Inciarte returned in mid-July.

Because Peralta sat regularly against lefties for the first two months of the season, his rate of plate appearances with the platoon advantage has predictably increased from 77 percent in 2014 to 82 in 2015, the latter of which is about the league average mark for left-handed batters the last two years. The league average is naturally going to be slightly higher than the rate for every-day starters because of late-inning pinch-hitters, but Peralta's rate stats haven't been heavily inflated by getting an unusual number of hacks with the platoon advantage.

The odds are that David Peralta won't continue to hit like one of the best hitters in baseball the rest of the way or into next season. More consistent playing time against same-side pitchers should eat slightly into his overall numbers, and despite some encouraging exit-velocity numbers, it's still reasonable to assume that he's had good fortune on his balls in play this season.

But the odds were never in favor of Peralta even reaching the majors. It was only two years ago that he even got his first taste of hitting in affiliated baseball. Now we're talking about a player who not only made the necessary adjustments to make the climb up the minor-league ladder in a year and a half but one who has already made adjustments to major-league pitching that have yielded legitimate improvements on the field.

Chris Mosch is an author of Baseball Prospectus. Follow @chris_mosch
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