Zack Godley could be a phenomenal reliever

Let's start with a blind comparison. The following pitchers play for the Diamondbacks and are named Zack G.

PITCHER A: 86 DRA-, 89 cFIP

PITCHER B: 100 DRA-, 95 cFIP

Pitcher A, obviously, is Zack Greinke. He signed a six-year contract for $206.5 million last offseason, and he pitched like an ace in the first year of that deal, with 4.0 WARP in only 158 ²⁄₃ innings. No one else on the Diamondbacks — and few others on the planet — can hope to excel like Greinke does. To even insinuate that he'd performed at such a pedestrian level is an insult to his otherworldly talent.

But! That doesn't mean we should ignore Pitcher B. While Zack Godley doesn't have Greinke's skill — or the salary to match — he came on strong in 2016. The Arizona bullpen looks pretty weak for 2016, without stalwart Brad Ziegler to anchor it, so it could use a formidable righty like Godley in the late innings.

Let's back up for a moment. Who, exactly, is Zack Godley? The Cubs drafted him back in 2013 and assigned him to relief; in the Chicago organization, he didn't start a single game. Then in December 2014, he came to the Diamondbacks as part of the Miguel Montero trade. He enjoyed a prosperous 2015 in the minors, with a 2.71 ERA across 99 ²⁄₃ frames, and when Arizona gave him the call, he thrived — his 3.19 ERA was better than rookie sensation Noah Syndergaard.

That success wasn’t meant to last, though. Godley’s peripherals — chiefly a 4.33 FIP — betrayed his mediocre true talent. And indeed, he allowed a lot more runs in his sophomore season: Only four other pitchers with at least 70 innings had a higher ERA. The struggles Godley encountered in the rotation (48 innings, 7.31 ERA) pushed him to the bullpen, where they largely continued (26 ²⁄₃ innings, 4.73 ERA).

But that’s not the whole story. Just as Godley got lucky in 2015, he was pretty unlucky in 2016 — the aforementioned DRA- and cFIP bore out his underlying ability. And he actually did pretty well as a reliever, tallying a 23.2 percent strikeout rate, 7.1 percent walk rate, and 64.4 percent ground ball rate. In particular, two elements of his relief performance make him a possible breakout candidate for 2017, should he sustain them.

For the first facet, let’s go with another blind comparison. The following players are well-coiffed relief pitchers.

PITCHER A: 40.7 percent O-Swing rate, 52.7 percent Z-Swing rate

PITCHER B: 42.7 percent O-Swing rate, 56.6 percent Z-Swing rate

For context: MLB averages in 2016 were 30.6 percent O-Swing and 63.9 percent Z-Swing.

Player A is Andrew Miller, the Indians lefty who mowed down the opposition in 2016. As FanGraphs’ Jeff Sullivan laid out back in June, Miller’s dominance had a simple cause: Hitters swung when he threw the ball outside the strike zone, and didn’t swing when he threw it inside the strike zone. The difference between his O-Swing and Z-Swing rates was the highest in the majors by a mile.

Miller regressed toward the mean over the later months of the year, but he still led MLB in that regard. The runner-up, meanwhile, was a familiar face:

Yup: Player B is Godley himself. As a starter, Godley put up a 30.3 percent O-Swing rate and a 64.6 percent Z-swing rate — pretty much in line with the major-league averages. As a reliever, though, Godley had the highest chase rate in the majors, along with the 15th-lowest swing rate in the zone.

What made Godley so deceptive once he moved to the bullpen? This is where the second facet comes in. He leaned on his breaking ball a lot more often, and for good reason — nobody could catch up to it:

While in the rotation, Godley averaged 82.2 mph on the curve, putting him in the top 10 percent of starting pitchers. And that velocity served him well: Only Jose Fernandez, Lance McCullers, Jon Lester, and Carlos Carrasco had a higher whiff rate on the pitch than Godley (20.9 percent). Upon becoming a reliever, he bumped his velocity up a tick, to 83.2 mph, and unlocked his true potential.

The craziness of Godley’s curve shouldn’t obscure the quality of his two hard pitches. When he first debuted back in 2015, Baseball Prospectus’s Chris Crawford wrote that “he doesn't have elite stuff, but he can miss bats in large part because nothing he throws is straight.” Indeed, both Godley’s cutter and sinker displayed a ton of arm-side break, which helped them fool both righties and lefties. Along with the curveball as an out pitch, Godley has all the ingredients to become a top-flight relief pitcher.

In all likelihood, Godley never would have lasted in the rotation — he can only dream of having Greinke’s stuff and command. Yet like so many before him, he blossomed into a star once he shifted from starting to relieving. Not many bullpen arms can deceive hitters, or throw them a curveball, like Godley can. As the Diamondbacks head into 2017 with the 25th-ranked bullpen in the majors (according to FanGraphs), they should rely on this righty in the late innings.

Ryan Romano is the co-managing editor for Beyond the Box Score. He also writes about the Orioles for Camden Depot, sometimes. Follow him on Twitter if you enjoy angry tweets about Maryland sports.