Diamondbacks’ Merrill Kelly expected to miss more than a month

The Diamondbacks placed Merrill Kelly on the 15-day injured list Tuesday evening due to a shoulder strain. After Tuesday’s 14-1 drubbing of the Cardinals, manager Torey Lovullo said the Snakes expected Kelly to be out for an extended stretch.

“We’re not looking in terms of weeks as what we had hoped for,” Lovullo admitted (link via Theo Mackie of AZ Central). “So I think the next step up is a month, more than that.”

While the manager said that surgery is not under consideration, he was noncommittal when asked if Kelly would be back before the All-Star break.

It’s another hit to a rotation that’s already without Eduardo Rodriguez until at least the end of May. Arizona’s biggest offseason signee suffered a lat strain in spring training. A recent setback resulted in a move to the 60-day IL. The D-backs subsequently signed Jordan Montgomery to offset some of the impact of losing Rodriguez, yet Kelly’s absence adds more uncertainty to what is arguably the team’s weakest area: rotation depth.

Zac Gallen, Montgomery and Brandon Pfaadt will hold the top three spots. Ryne Nelson opened the season in the rotation before taking a comebacker off his elbow and landing on the IL last week. Slade Cecconi and Tommy Henry seem like the top options for the Nos. 4 and 5 spots until Nelson returns. There’s very little experience behind them.

Cristian Mena and Blake Walston are on the 40-man roster but have yet to make their MLB debuts. Humberto Castellanos and Konnor Pilkington have limited big league experience and are in the organization as non-roster players at Triple-A Reno.

No one from that group can be expected to come particularly close to matching Kelly’s reliability. The veteran righty has allowed fewer than 3.40 earned runs per nine while reaching 30 starts in each of the past two seasons. He’d gotten out to another excellent April, working to a 2.19 ERA in his first 24 2/3 frames.

The defending NL champs have had a pedestrian start overall, posting a 12-13 record. They’ll hope a talented lineup keeps them in the playoff mix until their rotation gets closer to full strength. Rodriguez and Kelly could be back well in advance of deadline season, but an extended absence from one or both may increase the pressure on the front office to upgrade the starting pitching this summer.