CREATE TABLE table_5818 ("Date" TEXT, "Tournament" TEXT, "Surface" TEXT, "Opponent in the final" TEXT, "Score" TEXT)

What opponent in the final has rockford, Illinois as the tournament?
SELECT "Opponent in the final" FROM table_5818 WHERE "Tournament" = 'rockford, illinois'
SELECT "Opponent in the final" FROM "table_5818" WHERE "Tournament" = 'rockford, illinois'