Paul Pierce during his final season with the Celtics in 2013. BOSTON (AP) - Paul Pierce is retiring as a member of the Boston Celtics. Pierce helped bring Boston a championship in 2008 as part the Big Three of Kevin Garnett and Ray Allen. It's an honor to have this opportunity to once again call myself a Boston Celtic, Pierce said in a statement. Celtics managing partner Wyc Grousbeck said the franchise was honored that Pierce had chosen to retire as a Celtic.