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3/22/2014 5:36 A.M. ET

Delgado, Bradley battling for fifth-starter role

SYDNEY -- The D-backs haven't decided who will be the No. 5 starter in the rotation.

The two candidates, according to D-backs GM Kevin Towers, are Randall Delgado and top prospect Archie Bradley.

Because of the unique Opening Series in Australia, the D-backs were able to carry a 28-man roster, with three of the spots being starting pitchers who remained in Arizona. Without the need to carry more than two starting pitchers, the D-backs will play this series with 10 relievers.

After a strong start to the spring, Bradley has struggled in his past two starts, including Friday night against Team Australia.

"His first two were outstanding," Towers said of Bradley. "Last couple looked like he struggled a little bit with his fastball command, falling behind and wasn't landing his breaking ball as much as he needs to. The first two, that's all he did was pound the strike zone."

Bradley is likely to get one more start before the stateside opener on March 31, and the team will work to get Delgado stretched out next week.

There is only one rotation spot open, but that could change if veteran Bronson Arroyo has a setback in his recovery from a bulging disc.

D-backs wait to decide on backup catcher

SYDNEY -- Tuffy Gosewisch was on the Opening Day roster as the D-backs' backup catcher, but the battle for the job will continue once the team returns to Arizona next week.

Gosewisch was already on the 40-man roster, while veteran Henry Blanco was not, which was one of the factors working in Gosewisch's favor. Had the team put Blanco on the roster, his contract would have become guaranteed for the entire season.

This way, the D-backs maintain their options heading into the March 31 stateside opener against the Giants.

"Tuffy's been playing very well right now," D-backs GM Kevin Towers said. "If you add Henry you kind of lose a little of your flexibility. We have another week to kind of evaluate things and decide what we do before the Giants series, and then we're kind of locked in if we go with Henry at that time. It buys us a little more time before we have to make a decision. We felt we needed a little more time to figure out which way we wanted to go."

This is Gosewisch's first Opening Day in the big leagues. The 30-year-old made his big league debut last year after more than eight years in the Minors.

"It's only been about 10 minutes since I found out, so it's kind of hard to put into words," Gosewisch said just prior to the D-backs' scheduled matchup with the Dodgers at Sydney Cricket Ground. "This is the goal of everybody. It took a while, but I couldn't be happier."

D-backs need to trim bullpen before U.S. opener

SYDNEY -- The D-backs have some tough decisions to make with regards to their bullpen next week.

For the Opening Series with the Dodgers, the D-backs were able to carry 10 relievers, but they will have to cut down to seven for the March 31 stateside opener with the Giants.

If Randall Delgado claims the injured Patrick Corbin's spot in the rotation, that would leave nine relievers, and it appears that Bo Schultz will head to Triple-A after the Australia trip.

Addison Reed, J.J. Putz, David Hernandez, Brad Ziegler, Josh Collmenter and Oliver Perez all but certainly have spots locked up, leaving a battle between lefty Joe Thatcher and righty Will Harris for the final spot.

Harris has pitched well this spring and did a nice job for the team last season.

Thatcher, meanwhile, struggled early in spring, but has pitched better of late.

One thing working in Thatcher's favor is that he is out of Minor League options, while Harris is not. That means the D-backs could option Harris down to start the season, and he could provide insurance should any of the other relievers falter or get injured.

Worth noting

• Towers said despite the injury to Corbin and the uncertain status of Arroyo, he is not actively looking for starting pitching on the trade market.

"We're not aggressive or feel like we've got to go out and get another starter," Towers said. "I don't see us really making a trade or signing another pitcher before the Giants series. I think we're just going to stay in house."

• The D-backs chose to go with outfielder Tony Campana rather than outfielder/infielder Matt Tuiasosopo for the final spot on the bench.

"Gives us another left-handed bat off the bench. It gives us speed off the bench," Towers said. "We've seen what his legs can do late in the ballgame. I think Campana earned a spot on the ballclub the way he played this spring."

• One of the buses carrying a few D-backs players and support personnel got a flat tire on the way to Sydney Cricket Ground on Saturday and the group had to walk about a half-mile to the stadium.

• Outfielder Cody Ross will be eligible to come off the disabled list on April 3, but Towers said it is likely he will need to go to Triple-A Reno for a rehab assignment since there will be no Minor League games for him to play toward the end of next week and he cannot play in Cactus League action because he has already been placed on the DL.

"I don't know if Cody is going to be really ready as soon as he's able to come off," Towers said. "It probably wouldn't be a bad idea at some point to get him to Reno or somewhere once their season opens up April 3, just to play in some games."

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.