Diamondbacks Rotation Projection and Upcoming Roster Decisions

The Arizona Diamondbacks are about to see the return of injured starter Jordan Montgomery. He’s been out with right knee inflammation since late June. Montgomery is expected to slot into the rotation on Tuesday in Kansas City against the Royals.

At that point the D-backs will have five starters on the roster, with Montgomery joining Zac Gallen, Brandon Pfaadt, Yilber Diaz, and Ryne Nelson.

Once Montgomery comes back there will need to be a roster move. The two most likely options would be to either option Humberto Castellanos back to Triple-A Reno, or DFA Thyago Vieira. Both pitchers are low leverage relievers.

It should be noted that Montgomery will make two starts before the July 30th trade deadline. As I wrote a few days ago, evaluating how those starts go will be a key to deciding whether the D-backs pursue a starter by July 30th. The upcoming starts for Yilber Diaz and Ryne Nelson will also factor in heavily in Mike Hazen’s decision making.

Speaking to Steve Gilbert of MLB.com, Hazen confirmed that thought process

“I think if I feel very confident when Monty comes back and then (Kelly and Rodriguez) are right around the corner, I probably wouldn’t place as much emphasis on it. But I don’t know. It obviously depends on if Nelly and Yilber keep throwing the ball really well, that’s going to impact how this goes.”

Both of these pitchers will throw a bullpen session on Saturday, and are expected to throw one more bullpen session after that before facing live hitters in a competitive setting.

Once they start throwing simulation games, and subsequently progress to actual minor league rehab starts, they should pitch every five days with normal bullpen sessions in between.

We tentatively project Rodriguez to return either at home against the Phillies between August 9-11, or if the D-backs prefer a softer landing, August 12th against the Rockies. As for Kelly, he could be a week behind, returning during the Tampa Bay Series August 16-18. That’s what Kelly has been targeting all along.

While these projections are speculative, it can be stated with a high degree of confidence that the return dates won’t be any earlier than mentioned above. Any kind of a setback, or need to build in extra days due to soreness simply pushes out these dates.

In a perfect world scenario, there are no further injuries, Nelson and Diaz keep pitching well, and Rodriguez and Kelly have successful, effective returns. As unlikely as all of that happening seems, let’s take a look at What if.

The D-backs could opt to go with a six man rotation for a couple of turns through the rotation. That’s not a strategy they would be likely to deploy for any long term period, but it could be a useful way to keep everyone moving forward while not overtaxing them in the run up to September.

Another option would be to use the “Piggy Back” method for a couple of turns through the rotation. In such a scenario, Rodriguez or Kelly may be limited to three or four innings for a couple of starts, and one or both of Nelson and Diaz assume a long relief role.

Ultimately most of these situations tend to work themselves out naturally, but we know that the Diamondbacks’ front office and coaching staff are not above utilizing their creative minds to come up with solutions.