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04/09/12 10:10 PM ET

Barton slated for full-time duty upon return

First baseman activated, Allen designated for assignment

OAKLAND -- For all the talk made of the A's first-base competition over the past two months, it appears one may have never truly existed.

The winner, all along, was Daric Barton. Brandon Allen and Kila Ka'aihue were simply alternate options, until Barton was deemed healthy. That time came Monday, when the A's reinstated Barton from the 15-day disabled list and designated Allen for assignment.

"From this point on, we expect Daric to be the everyday first baseman," manager Bob Melvin said. "We feel confident about it, or he wouldn't be here at this point."

Barton was immediately inserted into the lineup, batting seventh against the visiting Royals and playing in his first game with Oakland since June 21, 2011, when he was demoted to Triple-A following an unfavorable offensive start. He was hitting .212 with zero home runs in 67 games at the time and appeared in 17 more with Sacramento before hitting the DL with a strained right shoulder.

Barton, 26, underwent surgery on the shoulder in August, and the A's are expecting his old self back now. They believe his injury largely affected his performance last season, which brought about a career-low .325 on-base percentage. The year before, in his only full season in the big leagues, that number was at .393.

Getting on base remains Barton's priority, though Melvin suggested it's nice to know he has the potential to hit one out every now and then. He has 26 career home runs in 438 Major League games.

"I'm not going to be like [Yoenis] Cespedes and hit 'em off the center-field façade, but if I run into them, I run into them," Barton said, smiling. "I'm not going up there trying to hit home runs, just going up trying to hit the ball."

"He's a good defender -- actually, a great defender -- and an on-base guy that's going to make our offense better," Melvin said.

The A's have always held Barton -- acquired in the 2004 Mark Mulder trade -- in high esteem, and the infielder is not blind to the patience they've demonstrated with him.

"I think they've been real loyal to me ever since I came over here, and it's something that you can't really expect to happen, but it's something that's happened," Barton said. "I've been real grateful for every opportunity they've given me, and I'm just going to go out there and show them what I can do now."

Barton did not appear in a spring game until March 12 and, in seven games, hit just .176 with a double. But in a four-game stint with Sacramento, he managed to collect seven hits in 19 at-bats, including a double, triple and, on Sunday, a grand slam. Hitting has not affected his shoulder -- in fact, Melvin believes his swing velocity has increased -- like the way fielding has. Barton said he still experiences stiffness in the shoulder while playing first base but noted: "It's just something I'm going to have to deal with."

"It gets stiff in colder weather, but it's something I'm going to have to work through and play through and do what I can to get the job done," Barton said. "I knew it would be stiff and sore, but once the adrenaline gets going through my veins, hopefully some of that will go away."

Barton said he will "save his bullets" when making throws and that the toss to second during a double play remains his focus, as the first one he made in Sacramento sailed into left field. Since, Barton has made some adjustments he hopes will translate to the big-league scene, as he continues an adjustment process with his shoulder.

The A's are likely to be cautious when it comes to deciding how many consecutive days he can handle fielding. Monday marked his fifth game at first base in a row, yet Sacramento had an off-day in between that time. Oakland, too, has an off-day Thursday, which should help Barton along.

Meanwhile, the A's have 10 days to trade, release or pass Allen through waivers. He's an intriguing option for clubs on the lookout for a first baseman with power potential, having compiled 142 home runs and 534 RBIs in 807 Minor League games over eight seasons. He hit .314 with two home runs and 14 RBIs this spring and, in three games with the A's, including an Opening Day start and two against Seattle ace Felix Hernandez, he went 0-for-7 with five strikeouts.

Fellow left-handed hitter Ka'aihue has received just one start -- with three appearances overall -- and is 3-for-8 following a spring campaign that resulted in a .250 average and three home runs in 17 games.

"It was a tough decision," Melvin said. "I've grown pretty close to Brandon here in a short time. The start he got off to was terrific, and then he went a little downhill. This spring, we asked him to do some things offensively, do something different in his swing, while he was trying to battle for a spot, which is difficult to do.

"Kila was just playing better at this point in time. We knew Daric was coming at some point and we were going to have to make this decision. I think it was more about how Kila was playing right now, as opposed to Brandon."

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.