 -- KANSAS CITY, Mo. -- Adam Dunn trekked 14 seasons and 2,001 games just to get to the postseason. But when his one and only playoff chance arrived Tuesday, he never got off the bench, and afterward he said he will retire.

The Oakland Athletics designated hitter, 34, told ESPN's Pedro Gomez that he has played his final game.

"I guess the computer got me," Dunn said, referring to the A's "Moneyball" tactics.

Long past midnight, after the Athletics' 9-8, 12-inning loss to the Kansas City Royals in the American League wild-card game, Dunn refused to take off his uniform, sitting in a back room instead of the clubhouse with most of his teammates.

He seemed to be soaking in the atmosphere one last time, even as the air around him was laced with disappointment.

When Dunn was traded to the A's in August from the Chicago White Sox, he said the final five weeks of the season would be his last hurrah. In the environment of an A's team grinding its way toward the playoffs, Dunn seemed to back off the retirement stance.

However, after a productive few games with the A's, Dunn's contributions were more like they had been with the White Sox, when he failed to reach base as often as he had in the past. Dunn batted .212 with a .316 on-base percentage for the A's and hit two home runs with 10 RBIs in 25 games.

When it came to Tuesday night's game against the Royals, the A's prioritized defense over the potential for more scoring chances with a surprise starting lineup. Manager Bob Melvin put Sam Fuld in left field and Geovany Soto at catcher, two obvious nods to defense. The ripple effect knocked Dunn from the lineup. Stephen Vogt was at first base, leaving Brandon Moss in the designated hitter spot.

Dunn also was 7-for-35 (.200) with 16 strikeouts in his career against Tuesday's Royals starter, James Shields.

Melvin went out of his way Tuesday afternoon to inform Dunn of the decision.

"I let him know what we're looking at so he's not surprised when he sees the lineup," Melvin said. "All our guys know that we do things a little differently here at times. We're trying to play for the day."

Dunn played for the White Sox from 2011 until the August trade and also played for the Washington Nationals and Arizona Diamondbacks after starting his career with the Cincinnati Reds. He was a two-time All-Star, in 2002 and 2012.

Dunn ends his career with a .237 batting average, 462 home runs and 1,168 RBIs but a zero in the postseason games played column.