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3/27/2014 7:53 P.M. ET

Bradley loses bid for rotation, sent to Triple-A

SCOTTSDALE, Ariz. -- The D-backs reassigned top prospect Archie Bradley to Minor League camp Thursday, ending his bid to win a spot in the starting rotation.

The move was not unexpected given the struggles the right-hander experienced in his last two outings after he was impressive in his first two spring starts.

"I'm not necessarily saying I saw it coming," Bradley said. "I wanted to be here as long as I could, and I think I did that. I understand being sent down for some things I need to work on and get better at. It's part of it, so go take care of business and get back up here."

Bradley, ranked by MLB.com as the game's top pitching prospect, will start the 2014 season with Triple-A Reno.

"We put a lot on him, we asked him to try a lot of things," manager Kirk Gibson said. "He tried them. Overall, I thought that the right thing is to send him back to the Minor Leagues and finish off. We want him to stay here when he comes. He's just got some things to simplify and finish off. He's close."

The biggest things Bradley needs to work on is his fastball command and the improvement of his changeup.

"I think I can compete there now," Bradley said of the big leagues. "That's just the way I am, but at the same time, I look at what I did this spring and there's still some things I need to polish out and get better at. I think this is what this is all about, go down there and prove to them that I can do that and then everything will work out."

D-backs holding out to make final roster decisions

SCOTTSDALE, Ariz. -- The D-backs will likely take their final roster decisions down to the wire following Saturday's final exhibition game at Chase Field.

The only roster move the team announced Thursday was the reassignment of prospect Archie Bradley to Minor League camp. Past that, manager Kirk Gibson was playing his cards close to the vest.

In fact, Gibson did not say that Bradley's demotion meant that Randall Delgado was the No. 5 starter, despite the fact that general manager Kevin Towers said last week that the battle for that spot was likely down to those two.

"He's still in camp," Gibson said of Delgado. "Bo Schultz is still in camp as well. [Josh] Collmenter's still in camp. There's still guys in the mix."

The D-backs have to decide between Chris Owings and Didi Gregorius for the starting shortstop job, as well as whether Henry Blanco or Tuffy Gosewisch will be the backup catcher.

It's possible the D-backs could carry both Owings and Gregorius while outfielder Cody Ross opens the year on the disabled list.

Gibson also raised the possibility Thursday that the D-backs could go with just one of those two and instead carry an extra reliever in place of Ross.

It does look like the D-backs will carry two lefties in the bullpen to start.

"I'd say we're leaning toward two," Gibson said. "I don't know if the final decision has been made."

Worth noting

• Ross played four innings in a Minor League game Thursday.

While Ross is eligible to come off the disabled list in time for the April 3 game against the Giants, the D-backs are leaning toward having him play at least a few games for Triple-A Reno on a rehab stint.

"I'm itching to get back, but at the same time you want to be smart about it," Ross said. "Those extra couple of days or two days are probably not a bad thing."

• Wade Miley allowed three runs on seven hits over 4 2/3 innings Thursday. It was a strange outing for Miley given that his previous one was a regular-season game against the Dodgers in Sydney, Australia.

"Maybe a little bit," Miley said when asked if it was weird to be pitching in a Cactus League game again. "But that that's not an excuse at all. I just wasn't executing pitches. I was leaving fastballs over the middle of the plate, really wasn't getting ahead, so I was leaving them in fastball counts so they were able to sit on things. Just wasn't very good."

• The D-backs have tough decisions to make for their final bullpen spots, which is a good thing because it will leave them with options during the season should they need to plug a hole because of injury.

"I think it's one of our strengths," Gibson said. "I feel confident there's people who are prepared to step up this year. Anybody's in play."

Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.