The move means Seattle will likely call up a player from the Minor Leagues to fill the spot Saunders vacated. There are a myriad of candidates in Triple-A Tacoma, including shortstop Chris Taylor, first baseman Jesus Montero, recently acquired outfielder Xavier Nady, infielder Nick Franklin and center fielder Abraham Almonte.
A corresponding roster move is expected on Thursday.
Adam Lewis is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.