 In 2010 , MLS , which has teams that play in both the United States and Canada , was allowed to enter eight of its U.S.-based teams in the tournament . The top six MLS teams from the previous season 's league table qualified automatically for the tournament , while the remaining two spots are determined by preliminary qualification matches . The eight MLS entries began play in the third round of the tournament . In 2009 , both Seattle Sounders FC and the Columbus Crew finished among the top six teams in MLS overall league standings and therefore qualified automatically for the third round of the 2010 U.S. Open Cup . 
