user: Question: What is the lowest tier for a postseason result of Quarterfinalist?
Columns: ['Season', 'Tier', 'Division', 'Pos.', 'Postseason', 'Cup Competitions']
Types: ['text', 'real', 'text', 'real', 'text', 'text']
Sample row: ['1998–99', 3.0, 'Liga EBA', 8.0, '–', '–']
SQL:

assistant: SELECT MIN("Tier") FROM "Table" WHERE "Postseason" = 'Quarterfinalist';