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2017 Arizona Diamondbacks Review: #14, Patrick Corbin

Has Patrick Corbin recovered to be a legit #3?

MLB: Miami Marlins at Arizona Diamondbacks Rick Scuteri-USA TODAY Sports

Date of Birth: July 19, 1989 (Age 28)

2017 Line: 33 G (32 GS), 189.2 IP, 4.03 ERA, 4.08 FIP, 178:61 K:BB

2017 Value: 2.9 bWAR, 3.0 fWAR

2017 Salary: $3,950,000, 3rd-year Arbitration Eligible in 2018

SnakePit Rating: 7.07

2017 Analysis

It was a tale of two halves for Patrick Corbin but as a whole, it was a great season all-around for Corbin, posting his highest innings total and WAR values since his breakout 2013 season (208.1 IP, 3.5 fWAR). Corbin really struggled in his first 12 starts, but really turned things around afterwards:

First 12 starts: 66.1 IP (5.5 IP/GS), 5.43 ERA, 5.22 FIP

Last 20 starts: 120.2 IP (6.0 IP/GS), 3.36 ERA, 3.45 FIP

The highlight of Corbin’s 2017 season probably came on August 17th, when he threw 8.2 scoreless innings against the Houston Astros with 7 strikeouts, including 2 against Jose Altuve:

So, how did Corbin achieve this excellent turnaround? Corbin made a handful of changes, from throwing his slider more, throwing less sinkers, and moving his location on the rubber, but there is one thing that stands out most of all: location. And it’s a pretty significant change:

Corbin First 12 Starts vs Last 20 Starts Location
www.fangraphs.com

(from pitcher’s perspective so RHB are on the right-side of the GIF)

I’ll summarize that GIF for you:

  • In his first 12 starts, Corbin was throwing the majority of his pitches in the middle of the zone (9.2% middle-middle, 9.6% low-middle) and a decent amount below the zone (4.8% - 6.5% - 8.8% - 5.0% in the bottom four “red” zones from left-to-right)
  • In the last 20 starts, Corbin started throwing less in the middle of the zone (5.8% middle-middle, 7.8% low-middle) and started to really bury his slider low and inside to RHB (3.9% - 7.0% - 8.4% - 8.9% in the same “red” zones from above)

These changes had two direct effect: Corbin started giving up far less homers (1.90 HR/9 vs 0.88 HR/9) and he found massive success against RHB:

  • First 12 starts: .387 wOBA, 16.3% K%, 37.9% Hard%
  • Last 20 starts: .325 wOBA, 20.6% K%, 29.4% Hard%

In other words, right-handed batters went from being Ryan Zimmerman (.387 wOBA), on average against Corbin to being Denard Span (.325 wOBA). That isn’t complete dominance of RHB, but it was certainly enough to turn Corbin into a very good pitcher.

2018 Prospects

Corbin’s 2018 prospects really comes down to if he can continue to pitch like he did in those last 20 starts. To put those last 20 starts into a full-season context, we’ll convert his 3.45 FIP to FIP- to adjust for park factors: 79. Over a full season, a 79 FIP- would have had Corbin tie for 11th-best in the majors with Chris Archer. Archer threw 201 IP (just slightly more than Corbin) last year with that 79 FIP- and finished with a 4.6 fWAR. I would say that this gives Corbin a realistic ceiling for next year of around 4-4.5 fWAR. In other words, if Corbin keeps pitching like he did in his last 20 starts over the course of a full season, he can approach a 4+ WAR season.

And if I had to wager a guess, I’d say that Corbin’s success could be sustainable. He threw a 3.28 ERA in those last 20 starts which included .323 BABIP, 76.4% LOB%, and 12.1% HR/FB%. None of those are unreasonable numbers and the .323 BABIP is on the higher side of things. It’ll come down to keeping pitches out of the middle of the plate, generating groundballs, and keeping up his success against RHB. If he does that, then Corbin is poised for a very strong 2018.

But is there room for growth? Absolutely. Corbin as achieved his success on primarily being a fastball-slider pitcher, though he does throw an occasional changeup. The changeup is a work in progress, but there have been some positive results:

Corbin 2017 Changeup Whiff Percantage
Brooks Baseball

The September data point is a bit misleading as Corbin only threw 14 changeups for the entire month, but the rest of the chart shows a promising trend for his changeup, peaking at 11.76% whiff percentage in August. The volume of changeups is still low (below 10% every month except for July), but if he’s able to get swinging strikes with the pitch, it’ll be a valuable tool against right-handed batters that are able to lay off his slider and sit fastball. Corbin doesn’t need this changeup, but its development can help him take another step forward.

All-in-all, Corbin looks to be yet another valuable starting pitcher in the Diamondbacks 2018 rotation. He doesn’t have quite the upside that Ray might have, but he surely looks capable of being a top 15-20 starting pitcher next season. Unfortunately for the Dbacks, Corbin only has one year of control left and is going to get expensive going forward. I’d like to see the Dbacks extend Corbin but if they don’t, expect to hear his name on the trading block.