Jim Horner has served stints as manager of minor league clubs in which Washington farm team system?
Jim Horner:  He was previously the pilot of the Class A Wisconsin Timber Rattlers (2006–2007), High Desert Mavericks (2008–2010; 2013) and Class AA Jackson Generals (2014-2015) all Seattle Mariners affiliates. Seattle Mariners: The Seattle Mariners are an American professional baseball team based in Seattle, Washington.
Seattle Mariners