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3/5/2014 7:20 P.M. ET

Corbin keeps building up to start in Australia

SCOTTSDALE, Ariz. -- Patrick Corbin had hoped to get five innings in on Wednesday, but other than that, the D-backs lefty was pleased with his start.

Corbin, who is scheduled to start the regular season opener against the Dodgers on March 22 in Australia, allowed a pair of runs on five hits while going four innings.

"I think my fastball command wasn't as good as it was my first outing and I think that's why my pitch count got up a little bit," Corbin said. "It's going to happen during the season, you're going to throw a lot of pitches in innings and obviously you want to minimize that, but it was good to go out there and build up some pitches, and have a couple of tough innings."

To compensate for his fastball command, Corbin threw his slider and changeup more.

Corbin will have two more spring starts before his Opening Day assignment.

"I feel like I'm where I need to be and I'll be ready for my start [in Australia]," Corbin said.

Arroyo receiving treatment for bulging disk

SCOTTSDALE, Ariz. -- D-backs right-hander Bronson Arroyo, who was scratched from his scheduled start on Tuesday, was diagnosed with a slight bulging disk.

Arroyo underwent an MRI on Tuesday afternoon and was given an epidural Wednesday morning by team physician, Michael Lee.

"He feels a lot better since he's had that," general manager Kevin Towers said.

It is the same disk that gave Arroyo problems in 2011, and doctors say he is supposed to limit his activity for the next seven to 10 days.

"They want it to calm down before he starts throwing again," Towers said. "Of course, Arroyo doesn't think it will take that long. Nothing they're concerned about. It's not a herniated disk. He did it running the other day, felt it running. It's not anything worse than he had before. [Lee] thinks as long as they hit the spot right with the epidural, he should be fine."

Towers said he did not believe that the injury means Arroyo will have to begin the regular season on the disabled list. The D-backs, though, may have to juggle their rotation alignment a bit. Arroyo had been penciled in to start one of the first games of the regular season series against the Giants starting on March 31, but the D-backs will likely push him back a bit from that.

"I mean this guy had Valley Fever and pneumonia last year and found a way to start the season with the Reds," Towers said. "There's ways we could cover it. I would say he's still going to have time to get a couple of starts before the start of the season."

Worth noting

• General manager Kevin Towers was impressed by what he saw from top prospect Archie Bradley on Monday night.

"Archie's velocity was good," Towers said. "Fastball command very good, threw some good breaking balls, pitched out of a tight jam."

• If Bronson Arroyo is forced to begin the season on the disabled list, Bradley, Randall Delgado and Bo Schultz would figure to be candidates to replace him.

Schultz was also impressive on Monday night in following Bradley to the mound.

"Velocity has been pretty consistent over the last year," Towers said of Schultz. "Slider is getting better, cutter is getting better, confidence is getting better. I think he's at a point now where he's probably feeling like he belongs."

• Reliever Brad Ziegler's wife, Kristen, gave birth to a baby boy -- Joshua Bradley -- on Wednesday at 1:04 a.m. MT.

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.