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Projecting a 2016 Diamondbacks rotation

Who might our starting pitchers be in 2016, and what can we expect from them?

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Aces old, aces new. Randy Johnson and Patrick Corbin
Aces old, aces new. Randy Johnson and Patrick Corbin
Mark J. Rebilas-USA TODAY Sports

We knew coming in that our starting rotation was a weakness, full of question-marks. We had players coming back from major surgery, others with little or no major-league experience. With less than a handful of games left, some of those questions have been answered. Yes, Patrick Corbin appears to be healthy. No, Jeremy Hellickson is not going to have a bounce-back year. But others have been raised. Is Daniel Hudson going to be a starter or a reliever long-term? Can Archie Bradley rediscover his mojo? All told, it seems we know little more about the 2016 rotation than we did on Opening Day, Still, let's see what it might look like, along with predicting how well it might do.

There's no doubt that it's an area in need of massive improvement. With less than a handful of games left, the 2015 starting rotation for the Diamondbacks has been worth 6.0 fWAR. That ranks Arizona 27th in the majors, and is on pace to be worse than it was last season, when it was worth 7.7 fWAR. This probably won't come as a shock, but the improvement we've seen is very heavily offense (and defense) driven: our WAR there has more than doubled, increasing from 11.0 to 24.0. With all the key participants there returning, that should take care of itself, meaning attention can be focused on pitching, and in particular, the rotation.

A stat you're going to see a lot here is FIP, so let's explain what this is, in case it's a new one. It stands for Fielding Independent Pitching, and is a way of measuring pitcher performance, taking defense out of the equation. As such, it uses only strikeouts, walks and home-runs, because fielders have little or no influence on those (the odd Pollock robbery allowed); it's scaled to "look" like ERA.. While I'm dubious of its merits as a measure of actual performance, what has been shown is that FIP is a better predictor of a pitcher's future performance than straight ERA, because it eliminates the randomness of batted balls and what happens to them.

On that basis, we can use FIP to rank the current potential starters we've used this year, and figure out which ones are likely to perform best in 2016. We've used 12 starters this season, though two of those were in only one game apiece, and for a total of less than six innings. I've included them here mostly for completeness, but we'll get to them in due course. The table is in increasing order of FIP.; xFIP, in case you're wondering (and I'm sure you are!), is a tweaked version of FIP, that also assumes a league-normal rate of home-runs per fly-ball, something else which can inflate or deflate a pitcher's actual numbers.

1 Daniel Hudson 1 3.1 0.00 1.94 1.94 0.1
2 Patrick Corbin 15 79.2 3.28 3.45 3.32 1.3
3 Robbie Ray 22 123.1 3.50 3.63 4.13 1.9
Randall Delgado
1 2.1 15.43 4.00 6.54 0.0
Chase Anderson
27 152.2 4.30 4.14 4.18 1.6
Jeremy Hellickson
26 141.0 4.60 4.35 4.21 0.9
Zack Godley
6 29.2 3.03 4.72 4.32 0.0
Rubby de la Rosa
31 185.2 4.56 4.76 4.07 0.5
9 Archie Bradley 8 35.2 5.80 4.96 5.16 0.0
10 Jhoulys Chacin 4 23.2 3.04 5.04 4.35 0.0
11 Josh Collmenter 12 68.2 5.24 5.08 4.64 0.1
12 Allen Webster 5 24.0 6.00 7.77 5.76 -0.6

In most of the case, you'll see that FIP is within a quarter-run of actual ERA, and as you'd expect, generally becomes more reliable as we get more data with which to work. The two pitchers with multiple starts who have the biggest difference between ERA and FIP are Godley and Chacin. They both have lower K:BB ratios, and have been lucky with balls in play (BABIP of .264 and .250 respectively, compared with MLB average of .298), so it would be optimistic to think their success is sustainable, if they maintain those strikeout and walk rates. Not to say they're useless, of course, just that I wouldn't expect either to continue posting an ERA around three.

The locks

With league average FIP sitting as close to four as dammit (3.99), there are two obvious pitchers who appear to have already booked their slots in our Opening Day rotation: Patrick Corbin and Robbie Ray, with FIPs of 3.45 and 3.63 respectively. Interestingly, both have had the same issue this year - not being able to pitch deep enough into games - though for obviously different reasons. For Corbin, it has been the result of his recovery from Tommy John, with the team understandably being cautious. That seems to have gone well, Corbin's velocity back to pre-surgery levels (a tad higher: 92.4 vs. 92.1 mph in 2013), so the training wheels should largely be off in 2016.

Ray's issues are different. Of the 120 qualifying pitchers in the majors, Ray is #1 for pitches per plate appearance, and it's not even close; the #2 (Ian Kennedy) is as far from the #14 as he is from Ray. The five and a half innings Ray has averaged per start isn't terrible, but somebody who is one of your top two pitchers should certainly be going deeper into the game than that. However, it's not necessarily fatal for a young starter. As shoe pointed out the other day, there was another D-backs pitching prospect who had similar problems at a year older than Ray, with exactly the same P/PA figure of 4.14. That pitcher went on to become Cy Young winner Max Scherzer.

The bullpen conversions

There are three players on the list above who have spent most of the season as relievers rather than starters. It's perhaps worth looking at their overall numbers, rather than just the starter ones: for Randall Delgado and Daniel Hudson, we have only one start, while Josh Collmenter performed a great deal better out of the bullpen, with a FIP there of 3.96. Delgado, too, was better than league average at 3.89. However, I don't know if we would want to return either man to the rotation. Collmenter, in particular, has shown significantly better numbers out of the bullpen, with an ERA there of 2.32, compared to above four as a starter. I think both are best served by relief roles.

The other one is Daniel Hudson, and is more intriguing. Hudson's overall FIP is 3.48, which would make him a better starter than anyone bar Corbin, and is also in line with his career figure of 3.56. He's another TJ survivor, and is now throwing much harder than he was: an average FB of 92.7 mph, compared to 88.5 mph in 2012. However, it's obviously easier to throw harder (as it were) coming out of the 'pen for a single inning. But it's almost a rule: if a pitcher is above average, he's more valuable as a starter, simply because he'll throw more innings. Though if using Hudson as closer in 2016 stops Dave Stewart from selling the farm to get Aroldis Chapman, that's certainly providing value as well.

It certainly appears to be Hudson's goal, saying earlier this month, "I’m going to prepare this offseason like I have every single offseason, like I’m trying to win a spot in the rotation. And if we decide not to do that, I’ll do something else." He does acknowledge that, having thrown only around 70 innings this year, it would be a stretch to expect him to go back to 200. "But I feel like being 29 and being around for a long time and being three years away from surgery, I can handle more workload than maybe you would think... If I do end up in the rotation, it’ll be a start-by-start thing. It’s going to be, ‘How are you feeling? Need an extra day?’ That kind of thing." I'm all for giving it a shot.


Clearly, there are alternatives, players who were not on the roster at all this season. It's generally believed the D-backs front office will look to add an upper-tier starting pitcher this winter, and there is also the prospect of help from within, most obviously organizational Pitcher of the Year, Aaron Blair, whom many expected already to in the major leagues. But I think I'll save those for another day! Based purely on what we have seen this year, let's select six starting pitchers to throw 27 games each; it will be a five-man rotation, but you never use just five [our five top guys have made a total of 121 starts, with seven others combining for the remaining 37]. By FIP, they'd be:

  1. Patrick Corbin: 3.45
  2. Daniel Hudson (career): 3.56
  3. Robbie Ray: 3.63
  4. Chase Anderson: 4.14
  5. Jeremy Hellickson: 4.35
  6. Zack Godley: 4.72

Weighting them all equally, that would average out at a FIP of 3.98, virtually dead on league average. As a yardstick, the Padres' rotation had a FIP of 3.99 this year, and their starting pitching was worth 10.1 fWAR, four wins more than the Diamondbacks. If we can simply avoid the "garbage starts" [Arizona's four worst starters by ERA, none of whom make the top six above, had 26 games and an ERA of 5.72], the signs suggest we could pick up those four wins, just by repeating this year's performances, and before taking into account any new additions.