OAKLAND — Daric Barton was in the dugout when the A’s won the American League West last year but admits he felt a bit like an outsider crashing a party.

Sunday, however, Barton not only was on the field when Oakland repeated as division champions, he was right in the thick of the victory and at the center of the midfield celebration.

“There’s nothing that tops today,” said Barton, who went 3-for-3 with a homer and a walk in the A’s 11-7 victory. “I feel like I’m more part of the team. I feel like I’ve done something to help the team win. So this is a great time in my life.”

The A’s have a lot of rags-to-riches stories in their clubhouse, but Barton may be “tops” among them.

Acquired in a 2005 trade with St. Louis, Barton has been in the organization longer than any player on the roster. But it appeared he was at the end of the line with the team this season after being designated for assignment twice, once at the end of spring training and again early in May when he hit .143 in a brief stint as an injury replacement.

When he went unclaimed, Barton stuck with the organization and kept plugging away at Triple-A Sacramento, waiting for one more chance. When he was finally recalled on Aug. 26, he returned a different player.

Starting 20 of the last 27 games, Barton has hit .319 (23 for 72), played a flawless first base and has been a major part of their September run to the finish line.

Now, it appears he will be part of the 25-man roster for the first round of the playoffs. Asked directly if Barton would be on the postseason roster, manager Bob Melvin said, “I don’t see how he can’t.”

Barton said he isn’t worrying about it.

“I’m thankful for being here this second, this day,” he said. “I’m going to embrace what we’ve got going on right now, and worry about what happens later, later.”

Said Melvin, “You could ask him, but in June, he’s probably thinking, ‘I’m not going to be part of this thing.’ But now, he’s not only part of it, he’s a big part of it. When he was called upon, he definitely was ready.”

General manager Billy Beane maintained that as long as Barton didn’t go elsewhere after he was outrighted, he was going to have a place in the organization.

“He’s always had the advantage of the G.M. being a big fan of his,” Beane said. “I think he has all the skills that sometimes don’t necessarily show up in the boxscore — he’s a tremendous defender, he’s a good baserunner, he’s got a great eye at the plate. And he’s really grown up a lot. To see him contribute and be part of these last few weeks has been great and satisfying for all of us in the organization.”

So what changed?

“It’s more off the field,” Beane said. “Daric has really matured. He had a hard time when he was younger handling things when they didn’t go right. He’d get frustrated with himself. Now he’s taking things and accepting that it’s not always going to be perfect.”

Barton confirmed that he has a new mind-set.

“I take it day by day,” he said. “Whatever happened in the past happened in the past. I live for today, and today’s been a great day. I couldn’t ask for a better day, especially with the ending we had here.”

Barton said he’s glad he hung in with Oakland. He said there was never a doubt that he would as long as the door was open to him.

“This is the only place I know,” he said. “This is where I’m comfortable, this is where I want to be. I couldn’t ask for anymore.

“I am proud of myself,” he added. “I realize the player I am now and I have all the confidence in the world in myself. If I just stay with my approach and just be me, I think I’ll be just fine.”