A former A’s outfielder will return to the club Thursday; Mark Kotsay will be announced as the team’s bench coach, The Chronicle learned late Wednesday.

Kotsay, 39, was a key member of the 2006 A’s team that made it to the American League Championship Series. Oakland obtained permission last week to interview Kotsay, who had another year left on his contract as San Diego’s hitting coach.

Mike Aldrete, a onetime Giants and A’s outfielder hired away from the Cardinals last year to be the A’s bench coach when Chip Hale became Arizona’s manager, will move to the open first-base coaching spot.

Kotsay has only one year of major-league coaching experience, but during his playing days, he was seen as manager material. A’s manager Bob Melvin has mentored future big-league managers, including Hale, Cincinnati’s Bryan Price and Milwaukee’s Craig Counsell.

After the A’s last-place finish this past season, The Chronicle reported that there were indications that clubhouse chemistry was an issue, with the team not really coming together after nine offseason trades. Kotsay isn’t much older than most of the A’s players and only three years removed from his playing days, and he has a reputation for leadership.

Kotsay also delivered one of the key hits in the past two decades of the A’s history, with a two-run, inside-the-park homer in Game 2 of the 2006 ALDS against Minnesota.

Susan Slusser is a San Francisco Chronicle staff writer. E-mail: sslusser@sfchronicle.com Twitter: @susanslusser