Davis returned to Oakland on Thursday morning after getting word that his girlfriend, Jill, went into labor. The couple is expecting a son.
With Davis gone, rookie Renato Nunez played left field in Oakland's 6-2 loss to Boston, drawing his first start since being recalled from Triple-A Nashville on Sept. 5.
Davis is sitting on 39 homers after tallying a career-high 42 during his first season with the A's last year. He also has a career-high-tying 102 RBIs.
Jane Lee has covered the A's for MLB.com since 2010. This story was not subject to the approval of Major League Baseball or its clubs.