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03/24/2013 9:47 PM ET

Nakajima will not play second base

PHOENIX -- After trying out Hiro Nakajima at second base for a day, the A's have decided to put that experiment on hold.

"Shortstop is his position," manager Bob Melvin said, "and my guess is he'll be there most of the time."

Nakajima played three innings at second base in a Minor League game on Saturday, and three at shortstop. Melvin was managing the big league club during this time, but said reports indicated Nakajima simply didn't look at ease at second.

"It was just something we wanted to try out, and that was the place to do it," he said. "When you go over to a different position, sometimes it's a little uncomfortable. I know he's comfortable at short, so we just wanted to take a look. He was good about doing it, and whether or not we do it again, I'm not sure."

It's highly unlikely Nakajima gets any playing time at second in a Cactus League game, with the position already being shared by five candidates, and the A's won't be apt to try him out there in a regular season game until he picks up more experience.

Nakajima started at shortstop on Sunday and went hitless with a walk in three at-bats, lowering his average to .150. Twice he put the ball in play on the first pitch.

"There's a possibility because I've struggled at the plate that I'm being overly aggressive," Nakajima admitted after the game through his translator. "When it's a strike I attack the ball early in the count. A takeaway is I'm actually really able to see the ball clear right now."

"It appears to me like he's getting more comfortable," Melvin said. "Certainly a nice three-hit day goes a long way for your confidence, and I know that day, when he gets a couple hits, it will be welcomed. He seems like he's on his way to one."

Melvin's club only has six spring games remaining though, and with each passing day it seems more likely that Jed Lowrie will get the starting nod at shortstop on Opening Day. Still, the A's are likely to keep Nakajima on the big league roster.

Weeks' demotion narrows second base field

PHOENIX -- Jemile Weeks was removed from the A's second base competition on Sunday, when the club opted to send him to Triple-A Sacramento.

The race still includes Scott Sizemore, Adam Rosales, Eric Sogard and Andy Parrino, with Jed Lowrie's name still in discussions, though he seems likely to start the season as the everyday shortstop thanks to the continued struggles of Hiro Nakajima.

The A's are likely to carry all five guys to the Bay Area next weekend for a preseason series with the Giants, but only three will make the roster, assuming Nakajima remains with the big league club -- and only two if Nakajima and new first baseman Nate Freiman make the team. Either way, one spot undoubtedly goes to Lowrie, who is hitting .310.

Sizemore has struggled to the tune of a .171 average this spring, while Weeks was far more impressive with a .370 mark. But the A's have been consistent in saying that between the two, Sizemore was going to get the lengthier look since he's playing catch-up after missing all of 2012. Weeks was also set back by a shoulder injury that forced him to miss two weeks of Cactus League action.

"It was tough," manager Bob Melvin said of demoting Weeks. "He's had a good spring, certainly offensively more than defensively at this point, but he's worked very hard on his defense and will continue to work very hard on his defense. It was a difficult cut, but we have to cut our numbers down at some point."

Should the A's deem Sizemore unprepared for regular season games before they set their roster, there's a possibility that Rosales and Sogard could form a platoon at second base. And if the decision comes down to choosing just one of those two players, Rosales holds the edge because he's out of options.

"Their versatility helps them out," Melvin said, "and they're having great springs."

The A's also optioned Shane Peterson to Triple-A on Sunday following an inspiring showing. The outfielder put together a .408 average in his first big league camp.

"He had an unbelievable camp," Melvin said. "All of the coaches just rave about him -- and probably didn't see him play his best position, which is first base. This guy is very close to being a big leaguer, and I feel he could play at the big league level right now."

Said Peterson: "That was kind of my main focus, trying to make a good first impression. Bob said numerous times they went through almost 50 guys last year, so there's a lot of opportunity."

Okajima happy to bide his time in Minors

PHOENIX -- The A's are soon likely to set their roster without Hideki Okajima's name on it, but the veteran reliever says he's fine with continuing his career in the Minors while waiting for a chance to pitch in Oakland.

"I'm completely fine with it," Okajima said Sunday. "I signed a Minor League contract, and I'm just happy to be pitching in America again, no matter where it is."

For three straight days Okajima appeared on the A's pitching list, but never got into a game. Finally, on Sunday, he was brought in for the seventh inning, and he stranded two on base, his ERA lowered to 5.19 by day's end.

Okajima has been spotty this spring, and he essentially needed to be perfect to have any chance of grabbing hold of a roster spot. He's one of 13 relievers vying for seven bullpen openings, three of which are already guaranteed to Grant Balfour, Ryan Cook and Sean Doolittle. The others are likely to go to the four relievers out of options: Jerry Blevins, Chris Resop, Pat Neshek and Travis Blackley.

This marks Okajima's first spring in Arizona, and it's presented quite the learning curve for the veteran.

"It's been tough," he said through a translator. "Compared to Florida, it's so dry, and the ball flies a lot farther here. I'm quite surprised at the difference. It's a good place to gain experience.

"I'm happy with the improvements I've made. … If the season started tomorrow, I would be ready."

Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.