When Diamondbacks fans (and management, and players, for that matter) woke up on the morning of December 4th, the assumption was that any news generated by the team would either be the signing of a middle of the rotation piece like Mike Leake, or just endless reaction pieces on the uniforms that had been unveiled the day before. Derrick Hall certainly didn't look like he had a major trick up his sleeve. Front office members of the Dodgers and Giants woke up that morning worrying about which of them would sign Zack Greinke, never suspecting what would transpire as the day went along. Before we were asleep, Greinke was a Diamondback, and the entire baseball world was shocked, probably more shocked than by any Diamondbacks signing since Randy Johnson chose the Diamondbacks over the Rangers, Angels, Dodgers, and Astros.
Recognizing that signing Greinke signaled that the team was in win-now mode, the Diamondbacks resumed trade talks with the Braves, stalled earlier when the Braves had asked for A.J. Pollock in exchange for Shelby Miller. When the dust had settled, the Diamondbacks got another key rotation piece, albeit at a very high price. Greinke and Miller form a very impressive top of the rotation, further bolstered by the return of Patrick Corbin from Tommy John surgery.
Fourth starter Rubby De La Rosa will be the only returning starter from last year's Opening Day rotation, as Josh Collmenter is in the bullpen, Chase Anderson and Jeremy Hellickson have been dealt elsewhere, and Archie Bradley failed to win the competition for the fifth starter job, being optioned to AAA Reno on Monday.
The battle for fifth starter seems to have been won by Robbie Ray, although Zack Godley still has an outside chance. With Bradley and Tyler Wagner being optioned, they are now eliminated from the competition, but will still likely appear with the big club at some point during the season.
How Do They Stack Up?
With the new acquisitions and Corbin's return, the Diamondbacks have a chance to go from one of the worst rotations in the major leagues (24th in Wins Above Average, or WAA) to top-half, or even top-five. Considering their position players finished second in the major leagues by WAA last year, this could be a key difference maker. The rotation as a whole was worth -3.1 WAA last year; Greinke has averaged 4.2 WAA over the past three years. Miller, while not pitching at nearly the same level as Greinke, has been around 2 WAA in two of the past three seasons, and hasn't been below average in his career. If Corbin can return to the form that made him an All Star in 2013, the top-three pitchers should all be solid at worst and great at best.
The back end of the rotation is a bit weak, though. In his first full season, Rubby De La Rosa was two different pitchers. He was lights-out against right handed hitters, holding them to a .214 average and .611 OPS. Left handed hitters were another story, though, as they hit .315 with a .949 OPS. There is hope that he can fix that problem, as he had not shown major splits at any level prior to last year, but it's hard to imagine he is that good against right handers again, as they likely won't have a .249 BABIP against him again this year.
As far as the winner of the fifth starter job is concerned, none of them have much experience, and that experience is very much a mixed bag. Robbie Ray, who appears to be the favorite at the moment, performed at around an average level with the Diamondbacks last year, but struggled to work deep into games. His six starts with Detroit in 2014 ranged from decent to terrible. Zack Godley was great in six starts last year, but he has never thrown 100 innings in a season, let alone the 150-180 you would like out of a full time starter,
There is decent depth, with last year's fifth starter Archie Bradley starting the year in AAA. He has struggled since coming back from being hit by Carlos Gonzalez's line drive last year, but he will look to fill in if anyone falters. Tyler Wagner made a spot start and two as a September call-up last year with the Brewers, generally performing poorly, although he did have a good outing against the Cubs on the penultimate day of the season. He has thrown 150 or more innings the last two seasons, so he is a nice depth piece, and will also start the season in AAA Reno.
The Diamondbacks should have an above-average rotation, possibly a top-ten rotation. But for them to make it into the top-five rotations in the league, Corbin will have to return to his 2013 form and either De La Rosa or whoever wins the fifth starter job will have to be a breakout star. If those happen, the Diamondbacks will likely have the best rotation in the division. If the rotation becomes Greinke, Miller, and the three stooges, the offense will have to carry the team.
On average, teams used 25 pitchers last season. Half of MLB teams had at least seven pitchers make at least ten starts, and only the White Sox, Mets, Cardinals, Cubs, and Padres had only five pitchers make at least ten starts. (Much was made of the injuries the Cardinals suffered early in the year and in Spring Training, but once the year started, their pitching staff was remarkably healthy, as only the Orioles, Pirates, and Giants used fewer pitchers over the course of the season.) Depth is of paramount importance.
The Diamondbacks are well stocked when it comes to rotation depth, although quantity appears to trump quality in this area. On the top-tier of the depth are the three who will lose the battle for the fifth starter. Anyone out of that group of four (Ray, Bradley, Godley, Wagner) could be expected to fill in for either the fourth or fifth starter without much of a drop-off. Behind that group is a second-tier, consisting of #2 prospect Braden Shipley, Cuban Yoan Lopez, and the reward in the Addison Reed trade, Matt Koch. All of these pitchers have the ability to get people out, but have no experience at the big league level and would represent at least a partial drop-off from the Opening Day rotation or from that first tier.
Finally, there are the guys who will be on the big league roster as bullpen pieces, but could make a spot start as needed. First on this list is Josh Collmenter, who has been an above-average starter in 2011 and 2014, and has provided above-average value in every one of his five major league seasons. Sure, he's struggled this spring, but he's still someone that can provide a decent start (possibly even 5 or 6 innings) in a tight spot. Randall Delgado, Daniel Hudson, and Andrew Chafin all have starting experience, and Delgado and Hudson both made spot starts last year, but they are not as likely to be used in that role, as they are likely to be splitting the key seventh inning bullpen spot, and wouldn't be stretched out, and Chafin might wind up the only left handed option out of the bullpen.
The Diamondbacks have the pieces for one of the best rotations in all of baseball. Zack Greinke and Shelby Miller were both top-25 pitchers in all of baseball last year, by fWAR. Patrick Corbin has top-end stuff on his day. Rubby De La Rosa and Robbie Ray both have a lot of potential, and can be unhittable at times. There is plenty of depth at the 4th or 5th starter level, so they will still be in good shape if either De La Rosa or Ray falter or suffer injury. The biggest concern for the rotation is if one of the top-three starters is injured or ineffective; there doesn't appear to be anyone that can step up and fill that role. Continued health for Greinke and Miller will be one of the biggest factors in whether or not the Diamondbacks contend in 2016. If all goes well, this is a top-five rotation. But if any of the top three starters don't work out, it could be another long season in the desert.