2017 Arizona Diamondbacks Review: #6, Zack Godley

• Date of Birth: 4/21/1990 (Age 27)
• 2017 Line: 26 G (25 GS), 155.0 IP, 3.37 ERA, 3.41 FIP, 165:53 K:BB
• 2017 Value: 4.4 bWAR, 3.5 fWAR
• 2017 Salary: $535,000 (arb-eligible in 2020)
• 2017 SnakePit Rating: 8.08

2017 Analysis

After two years of bouncing back-and-forth between the MLB and the minors, Zack Godley had a breakout year, quietly putting up a fantastic season with little fanfare (outside of AZ). What makes it truly amazing is that Godley didn't even start the season on the MLB roster, having made his first start on April 26th due to Shelby Miller's injury. Still, despite the late start, this was good for 18th in the MLB in fWAR and 17th in bWAR.

So what changed for Godley? Simply speaking, it was a surge in his strikeout rate, jumping from 17.9% to 26.3% in the course of a single year. That 26.3% K% was good for 15th among MLB starters (out of 75), which is approaching the "elite" category (and it wasn't a fluke, either as his SwStr% was 9th-best in the MLB). And how did he get to this elite strikeout rate? By changing his pitch mix:

Godley threw his curveball more than any other pitch in 2017. That is not something you can say about a lot of pitchers. In fact, according to FanGraphs, Godley's curveball usage (35.6%) was second only to Drew Pomeranz (37.0%) last year. Only two other pitchers were over 30%. Godley's curveball rated as the second best in the MLB last year in terms of run value (+2.40 runs per 100 pitches), which is pretty amazing that he is able to throw a pitch that excells on such a rate basis at the frequency that he does. Out of 107 pitchers that threw at least 200 curveballs last year, Godley ranked 6th in whiff/swing%, 14th in swing%, and 27th in GB%. That's pretty insane when you consider he throws his curveball more than every pitcher except one.

But there's more than just curveballs and strikeouts. There's also Zack Godley's groundball rate, which is also borderline elite and the 4th highest in the MLB (out of 75). Having a high GB% is great, but to pair it with a nearly-elite K% is pretty rare:

Sean Testerman

Generally speaking, the more to the right and the higher you are, the better you are (imagine a line that starts in the bottom-left corner and points to the top-right corner, generally speaking). Godley is nearly a perfect blend. As I've written before, having both high GB% and high K% is a very rare occurance, and one that leads itself to strong MLB success. Brandon Webb is the pen-ultimate example of this, though there are others that have found success in this manner. And now, Zack Godley.

All-in-all, this lead to a fantastic season for Godley. You would have hoped for more than 155 innings, but he also threw 28 in AAA. That combined total (183 innings) is a sturdy jump from the 156 he threw in 2016 and 136 he threw in 2015.

2018 Prospects

Amazingly enough, we've had Godley for three seasons (including the 155 innings last year), and he's still two full years away from being arbitration eligible. In other words, we have 5 years of Godley left under team control. If Godley is able to sustain a similar level of success for the next 4-5 years, he's suddenly going to become the team's most valuable asset.

There are reasons to believe that Godley's success is sustainable: you can't fake your way to a 9th-best SwStr% (which supports the excellent K%) and his GB% and BB% are consistent from prior years. His BABIP is lower than you'd expect for a groundballer, though it's stayed largely in line with his previous MLB exposure. This would be a main place to look if he's having struggles or an ERA higher than you might expect.

However, I do believe that Godley is likely near or at his ceiling, at least on a per rate basis. He already throws 4 pitchers and they're all good or great pitches. There is some speculation that Godley might want to throw his changeup more, but I can't see that vastly improving his line all that much. Godley did see a velo increase on his sinker and his curveball last season and I wouldn't expect him to increase it even further going into his age 28 season.

Where Godley is likely to see growth, if any, is if he's able to throw more innings. If you extrapolate 4.4 WAR at 155 IP to 200 IP, you get 5.68 WAR. That would have been 9th best in baseball last year. As expected, Godley started to wear down as the season went on, as seen in his velocity (April is only one start so it's a tad misleading):

The velo drop is a bit steeper than you'd want in an MLB starter, but as mentioned above, Godley has gone through some pretty extensive inning increases over the past few years, as he was a full-time reliever in 2014 in the Cubs system. If Godley's going to see significant improvements over the next few years, including 2018, it will likely be in the form of more innings rather than being better on a rate basis.

In 2018, Godley has the stuff to pitch like a borderline ace, e.g. Brandon Webb-lite. I expect him to remain a valuable member of our rotation for 2018 and beyond.