You need to use encodeURIComponent to encode the url
$("#loadTables").load("php/leagueTable.php?team="+encodeURIComponent(teamSelect));
The encodeURIComponent() method encodes a Uniform Resource Identifier (URI) component by replacing each instance of certain characters by one, two, three, or four escape sequences representing the UTF-8 encoding of the character (will only be four escape sequences for characters composed of two "surrogate" characters), reference.