Forecasting the D-backs’ future rotation after Zack Greinke deal

The Arizona Diamondbacks’ moves over the past eight months have made one thing clear: they are looking to get younger without rebuilding.

That means trading for Luke Weaver, a 25-year-old starter who had only one year under his belt as a consistent rotation piece, and Zac Gallen, a 23-year-old who’s only made seven career starts but has high, high potential, so much so that the D-backs felt him worthy of No. 1 prospect Jazz Chisholm.

It also means sending out Zack Greinke, the D-backs’ former ace who is still one of the better starters in baseball. But at the age of 35, it’s possible those labels start to be removed.

What the additions and subtractions lead to is next season, where Arizona has a rotation that didn’t seem to have enough guys in 2019 to possibly having too many in 2020, yet neither project to be the type of ace that Greinke was.

That’s a good problem to have.

Despite the D-backs hanging around, this season may not be relevant anymore. They do sit 3.5 games out of the wild card race, but a trade of their ace, unproductive offense at home, relievers making their major league debuts and a constant aroma of the .500 mark makes this team not feel like one destined for the postseason.

Which means the cards are pushed to the table for next season.

Pending any movement on the trade market in the offseason, Robbie Ray, Gallen, Weaver and Mike Leake are the good bets to be a part of the rotation in 2020. The latter three seem like the safest bets while Ray could be an unknown.

Weaver will look to continue the success he’s had in the 11 starts this season, and as one of the core pieces of the Paul Goldschmidt trade, figures to be part of the long-term plan as he’s under team control until 2023. Gallen follows a similar path; Chisholm wouldn’t have been traded for a gap-filler or short-term rental. Gallen has six more years of team control.

The Leake trade was about filling innings for this season rather than next, and the D-backs’ low number they’re paying him suggests little commitment to having him pitch a lot next season. But getting a pitcher who can eat innings and be a tad bit above average (102 ERA+ this season, two points above the metric’s average of 100) isn’t something you don’t want on your team. Leake is veteran who will have 10 seasons under his belt entering 2020. In a rotation that will be full of youth, that could be very valuable, and Leake has something to pitch for with his free agency after the season.

The last two spots are where a bevy of options remain.

First, we can cross a couple of options off.

Corbin Martin, one of the top prospects received from Houston in the Greinke deal, will miss all of next season with Tommy John surgery. He, like Gallen and Weaver, represents the young-yet-ready type players the D-backs covet but will figure to play a larger role in 2021 and beyond as Martin has at least five more seasons of control left.

Taylor Clarke showed some promise at times this season but was recently sent down thanks to a 5.46 ERA and 82 ERA+. With guys around his age that have more talent in the mix next season, the chance for Clarke to be a rotation guy may be over. A bullpen role could be an interesting option though. The D-backs have at least two more years of control with Clarke, so their options remain open.

That leaves the possibility of five candidates in the mix for a single rotation spot next season: Taijuan Walker, Jon Duplantier, Merrill Kelly, Alex Young and Taylor Widener.

Walker and Widener could perhaps be the most interesting two names.

Coming over in addition to Ketel Marte from the Mariners in 2016, Walker pitched well in nine starts in 2017, with a 3.49 ERA and a very good 135 ERA+. But Tommy John surgery in early 2018 and a set-back this spring has kept him out baseball activity. A fully healthy Walker, who at 27 next season is still young and fits the D-backs’ liking of young-yet-ready players, could be an effective option as the No. 3 or No. 4 guy. He’ll have to perform well to make his case though, as he’s a free agent after next season.

Widener might have less of a chance. Currently the D-backs’ 14th ranked prospect, Widener had high potential and praise coming into this season. But he’s been a disaster in Triple-A, posting an 8.18 ERA in 22 starts with Reno and is allowing batters to hit .326 against him. At 25, Widener is of the age to be MLB ready and fits the D-backs timeline with their other starts well. But in terms of talent and true baseball-readiness, Widener still might be a year or two away. Widener is about to enter his fifth season, so if Arizona doesn’t call up him in 2020, he’ll be eligible to leave the organization.

Duplantier is in a bit of his own category. Another highly-ranked prospect, Duplantier got his shot this season and was OK, posting a 4.32 ERA and a 105 ERA+. But that was just in eight games and three starts, and Duplantier never got another chance as a shoulder injury has kept him out since June.

Duplantier figures to be somebody who the D-backs will give another shot to next season, given the potential the club sees for him and his five years of team control. He ranked in FanGraphs’ top 100 prospects before the season at No. 87 overall.

The next group consists of surprising performers from this season in Kelly and Young.

Kelly has pitched a lot of innings this season for the D-backs and has been quite decent. He owns marks of a 4.52 ERA and a 99 ERA+ but has thrown 131.1 innings for a rotation that’s desperately needed them. For the D-backs to get decent out of a 30-year-old rookie on a flyer deal who pitched in Korea last season is something they will take.

Whether Kelly can continue that or not be surpassed by others is what determines his role next season. Even though it’s worked for the D-backs, a 4.52 ERA isn’t exactly stellar, and an ERA+ of 99 is below average. And at 30, Kelly would be one of the oldest guys in the rotation. He may not fit the D-backs’ timeline. They can get out of him after next season, as he signed a two-year deal back in December.

Like Clarke, a bullpen role could be an interesting option for Kelly next season, especially since 2019 wraps up two years of D-backs struggles in that department.

Young could be a different story. The 25-year-old burst onto the scene after his call-up and has produced immensely. He owns a 2.60 ERA and 170 ERA+ in six starts and one relief appearance. With production and youth, Young could be a prominent piece to the puzzle that is next season’s rotation. Like Kelly, the D-backs will have to figure out his role, as Young has at most two years left of team control.

Ray, despite possibly being a major player in next year’s rotation, is included in this mix of guys due to his lack of team control. The D-backs have a big decision to make as Ray will enter free agency after next season. He’s has been a critical piece of the last five D-backs seasons. He’s started 131 games and has produced at a good clip in those starts, owning a 3.88 ERA and a 114 ERA+. He’s an above-average, middle of the rotation starter.

The Greinke trade was seen by some to be a salary dump, as getting out of Greinke’s deal gives the team flexibility to possibly re-sign Ray.

But issues exist with Ray. Despite the good numbers, his walk rates run high and especially did so last season (Ray allowed 5.1 walks per nine innings). He’s shown some inconsistency, as he was good in 2015, bad in 2016, excellent in 2017 and has since middled out the past two years. While only 27, Ray will enter next season at 28 and the first season of his next contract at 29, and will likely not be taking a shorter-term contract, making him older than the pitchers the D-backs figure to fill next season’s and future years’ rotations with. With age comes possible decline but experience as well.

But the biggest number the D-backs have to evaluate with Ray is that impending contract’s worth. Arizona is leaving their options open with Ray, not committing one way or the other to him publicly yet. Perhaps the lack of a deadline deal of him showed some loyalty.

It will simply be whether they want to keep him around or not. Whether they do affects the rotation drastically in the future.

Letting Ray walk would put the youth movement in full effect. Next year, Ray, Weaver, Leake, Gallen and Walker or Duplantier likely form the rotation. In 2021, Martin could enter the picture as Leake’s contract will be up. If Ray re-signs, that would leave Kelly, Young and Widener as possible bullpen pieces as the rotation would feature Ray, Weaver, Gallen, Martin and either a re-signed Walker or Duplantier. If he leaves, Kelly or Young could see themselves back in the rotation.

Keeping Ray also acts as a safety net in case one or more of the younger pitchers doesn’t turn out.

Whether the D-backs keep Ray or not, they have many options for the rotation, most of whom are young and ready to go.  Just what the D-backs are looking for.