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03/29/2013 5:47 PM ET

One roster decision remains between Pearce, Jackson

SARASOTA, Fla. -- The Orioles moved one step closer to their Opening Day roster Friday, officially naming Jake Arrieta for the final rotation spot, solidifying their bullpen and leaving one more decision for the last bench spot in either Steve Pearce or Conor Jackson.

Arrieta will start the team's home opener for the third year in a row, with Brian Matusz -- a final rotation candidate -- returning to the bullpen, and right-hander Jair Jurrjens -- the other final candidate -- going to Triple-A Norfolk. Rule 5 Draft pick T.J. McFarland will join Matusz in the bullpen.

The 27-year-old Arrieta, who recorded a 1.56 ERA this spring, never doubted he would make the club.

"No, absolutely not," said the right-hander, who started Opening Day a year ago, but had a disappointing season in which he went 3-9 with a 6.20 ERA. "Whether that's cockiness or overconfidence, whatever you want to call it, that's just the way that I personally had to approach the situation, with that mindset, knowing that I had to go out and actually show it and not just know it in my mind. I think the combination of having that mindset and knowing I had to kind of prove myself helped me get to the point where I am now."

Ryan Flaherty was also informed Friday that he will make the club, as expected, with Wilson Betemit's injury opening up one more bench spot for either Pearce or Jackson. It's a close call for the organization, with both players making a solid impression this spring.

"To be able to help the team out, it was kind of my goal coming into camp and I'm excited to get the opportunity," said Flaherty, a Rule 5 pick a year ago, who will be on his second Opening Day roster. "You never know what's going to happen. You can give the best effort, and outside of that, it's out of your control, so obviously you hear things. You hear this and hear that. The thing I've learned is you can't control everything, so you've got to show up and play hard and be valuable to the team."

Pearce has appeared in 25 games, going 15-for-44 (.341) with six homers and 17 RBIs, while Jackson has played in 22 games, going 16-for-53 (.302) with three homers and six RBIs. They both provide the team with a backup option for first baseman Chris Davis, as well as outfield depth, and that decision could come down to the wire, although Pearce is believed to have a slight edge. The 25-man roster must be set by 3 p.m. ET on Sunday.

Outfielder Chris Dickerson was reassigned to Minor League camp Friday and is expected to play for Triple-A Norfolk.

The Orioles' bullpen will have eight pitchers, including three lefties -- Matusz, McFarland and Troy Patton -- to start the season. Darren O'Day, Pedro Strop, Tommy Hunter, Jim Johnson and Luis Ayala will also be on the Opening Day roster -- barring an injury or trade -- with Chris Tillman on the disabled list, allowing the team an extra roster spot for the first four games before he returns.

"I'm so happy, I'm ecstatic," McFarland said. "It's surreal. This is incredible. I can't really sum it up into words right now. It's a dream come true. Since 2007, when my career started, that's what I've been hoping for, and it finally happened. I'm just so excited."

Tillman's DL stay was backdated, and he will be activated and start the team's fifth game on April 6 at home against the Twins. He threw 81 pitches over five innings Friday and did not experience any more abdominal issues against the State College of Florida, allowing one run and striking out six with two walks.

"I think I'm ready [for April 6], especially after today," said Tillman, who finished his outing in the bullpen and was a little behind schedule after suffering the abdominal injury earlier in camp. "Big step for me. It's not the matter of pitches. It's the number of times you get up and down. That's a big reason I got up one more time in the bullpen."

Backup catcher Taylor Teagarden will also have a spot on the bench, along with infielder Alexi Casilla. Betemit and left-hander Tsuyoshi Wada will start the season on the disabled list, while right-hander Steve Johnson will be placed there shortly, as well.

Roberts in nine-hole for O's likely the norm

SARASOTA, Fla. -- Orioles second baseman Brian Roberts met with manager Buck Showalter prior to Thursday night's game to discuss batting ninth against Rays ace David Price in their Grapefruit League matchup. The assignment, which will happen on Opening Day, could very well be a familiar sight this season.

"We talked about moving forward for right now," said Roberts. "It could be 162 games for all I know. That's how we're going to begin it, and let's go from there."

"It's the right thing right now, we feel like," Showalter said. "I think as the season goes on, he'll move up. This is the best way for us to start right now and let him get his feet on the ground. The guy's really been out of action for a couple of seasons, and I think this will take a little focus off. I just want to create the best situation for him to get started, and we'll see where it takes us."

Roberts hasn't batted ninth in a Major League game since July 31, 2004, and he has hit atop the order in 1,115 out of 1,200 career starts. While Showalter hasn't made anything official, Nick Markakis is the most likely candidate to bat leadoff for the Orioles with Nate McLouth another option. If Roberts did have a problem with the move, he didn't show it Friday afternoon, joking with reporters that it was a "heated exchange" and he's now going to try to hit more home runs.

"It's a batter order," Roberts said. "I'm happy to be healthy and playing, and my job for the past 13 years had been to be the best leadoff man in the game I could be. And now I'll be the best nine-hole hitter I can be."

"I am who I am. It really doesn't matter where I hit. I'm going to do the same things I've always done, and all that changes is that you don't hit for an hour."

Showalter said Roberts didn't try to talk him out of it and thinks having the veteran as a second leadoff hitter of sorts gives the Orioles a well-balanced lineup.

"I think Robby, he sees what went on last year with the needs we had, and you can hit him about anywhere in the order," he said. "When you look at lineups, especially in the American League East, you look at how you stack up with other teams seven, eight and nine. And the batting order means one time around for sure. He might lead off some innings. I think it's the best way for him to get off [to a good start]. We're all going to have enough challenges as it is without creating some that we don't have to.

"I want to take some of the pressure off him and let him get started at something he hasn't really done for a couple of seasons."

Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.