The D-backs optioned right-hander Jon Duplantier to Triple-A Reno following his start Sunday afternoon against the Angels.

Duplantier allowed six runs on six hits in just 1 1/3 innings.

In four starts for the D-backs this year, Duplantier has a 13.15 ERA, having allowed 19 earned runs over 13 innings. The 26-year-old walked eight.

"We felt it was best to send him down to ultimately gain more control, to gain more command," pitching coach Matt Herges said. "Obviously, we were seeing a little bit lower velo as well, all things that we feel he needs to work on. I told him when he left, 'We’re not so focused on your velo, we’re focused more on commanding your pitches.'"

Duplantier's velocity has been down a bit this year, which has left him with less margin for error with his location.

Injuries have been an issue for Duplantier in the past, but Herges said that Duplantier told him recently that he's felt as good physically as he ever has.

That makes the velocity drop all the more curious.

"That’s the million-dollar question," Herges said. "I think some would think it’s mechanical, I think some would think he’s just trying to throw at a speed he can command better. We’ll find out. We’ll put it that way. We have some really smart people who are going to be on this, smarter than me, for sure. We’ll see biomechanically what’s going on. Maybe even the mindset part of it, maybe that’s contributing to it. This is a tough one. I don’t see anything [wrong] biomechanically personally. But I don’t have the eyes like a lot of people do that we have that are a part of what makes people move and how they can move more efficiently and how they can throw harder because they’re moving more efficiently. So that’s coming. We’ll figure that out here pretty soon hopefully."

The Arizona rotation has been decimated by injuries. Zac Gallen, Madison Bumgarner, Taylor Widener and Luke Weaver are currently on the injured list, which has manager Torey Lovullo scrambling on a day-to-day basis to patch it together.

Corbin Martin, ranked as the organization's seventh-best prospect by MLB Pipeline, was recalled from Reno on Monday.

The right-hander has made two starts for the D-backs this year and has allowed nine runs over nine innings. Command was a bit of an issue for him as well, with seven walks and eight strikeouts.

"We felt like he was ready to come back and help us," Herges said. "We love this pitcher. We love the stuff. We love his makeup. Obviously, every pitcher, unless they throw a perfect game, can command the ball better. I think he’s on the right track with that. He’s getting a better feel for what he’s doing, how he’s moving. His confidence is gaining. I loved what I saw in his eyes today. He’s ready to roll."